Question 1

Why do planes ask for airplane mode?

Accepted Answer

Mostly caution: many phones searching for towers at full power can make a buzz in pilots' headsets; modern planes are well shielded. Up high there's no good signal, so your phone hunts for a tower — at full power. From the sky it can reach dozens of towers at once, and hundreds of phones on board do it together.

Question 2

Why does a USB-C plug fit both ways (and USB-A only one)?

Accepted Answer

USB-C has mirrored rows of pins, so the phone and the charger can work out which way it is plugged; USB-A has one row. Old USB-A: one row of 4 pins on ONE side of a little plastic tongue — so it only fits one way (and somehow it's always the wrong way first ). USB-C: 24 pins in TWO rows of 12 — and the bottom row is the top row turned round.

Question 3

Why does an electric car still have a small 12 V battery?

Accepted Answer

The big battery is switched off when the car sleeps; a small 12 V battery runs the computers, locks and lights and wakes the big pack's contactors. The big pack holds about 400 volts (some cars 800 V). When the car sleeps, big switches cut it off — safe for crashes and repairs.

Question 4

Why does a power bank lose charge when you don't use it?

Accepted Answer

A tiny chip inside never fully sleeps and sips power, and the cell self-discharges about 1–3 % a month; heat makes both much faster — store it half full somewhere cool. Inside, a tiny chip never fully sleeps — it watches the button and the cell, sipping a little power day and night. The cell itself also leaks a little: about 1–3 % a month.

Question 5

Why do LED lights flicker on your phone camera?

Accepted Answer

Many LED lamps blink 100 or 120 times a second with the mains (or with PWM dimming); your eye blends it, but a fast camera shutter catches the dark moments as bands. Mains power flips direction 50 times a second (230 V · 50 Hz: India, UK, Europe) or 60 times (120 V · 60 Hz: USA, Canada). So many LED lamps dip in brightness twice per flip: 100 times a second (120 in the USA).

Question 6

Why does a microwave oven slow down your Wi-Fi?

Accepted Answer

Both use radio waves around 2.4 GHz; a little microwave leakage drowns the Wi-Fi signal nearby, so 5 GHz Wi-Fi or more distance fixes it. Both use radio waves around 2.4 GHz — the same band (a microwave oven uses about 2.45 GHz). The oven blasts about 1,000 W inside a metal box.

Question 7

Why does a phone get slower when its storage is almost full?

Accepted Answer

Flash memory needs free blocks to write and to shuffle data around; when it is nearly full the phone must erase and move blocks first, so saving and loading take longer. Phone storage is flash memory. It writes new data into EMPTY spots (pages).

Question 8

Why should you 'eject' a USB stick before pulling it out?

Accepted Answer

The computer keeps some data in fast memory (a write cache) and writes it to the stick a moment later; eject = finish writing first, so no file gets cut in half. When you save or copy a file, your computer often parks it in fast memory (RAM) first… …and writes it to the stick a moment later. The copy window can say "done" before the stick really is!

Question 9

Why does a laptop charger have a box in the middle of its cable?

Accepted Answer

The box is the power supply: it turns 230 V / 120 V AC from the wall into about 20 V DC, and keeping it outside keeps its heat out of the laptop. That box is the real charger — a power supply. IN: 230 V AC (India, UK, Europe) or 120 V AC (USA, Canada) — most work on 100–240 V.

Question 10

Why does your phone charge slower when it's almost full?

Accepted Answer

Lithium-ion charging has two stages: fast constant current up to about 80 %, then constant voltage where the current slowly tapers off to protect the battery. Stage 1: the charger pushes FULL current — fast, up to about 80 %. Then the battery hits its voltage limit (about 4.2 V per cell). The last 20 % often takes about half an hour! That's why many phones pause at 80 % and finish just before you wake up.

Question 11

How does an induction cooktop heat only the pan?

Accepted Answer

A coil under the glass makes a fast-flipping magnetic field; it drives eddy currents inside the iron pan, so the pan heats itself while the glass only gets warm from the pan. Under the glass of an induction cooktop hides a big flat coil of copper wire. Its current swings back and forth about 20,000 times a second — so its magnetic field flips just as fast. An ice cube on the glass next to it? It barely melts! Tip: if a magnet sticks to your pan, it works on induction.

Question 12

Why do old phone batteries swell up?

Accepted Answer

As a lithium-ion battery ages (heat, overcharging, damage) its electrolyte breaks down into gas that puffs up the pouch; a swollen battery must be replaced, never pressed or punctured. Inside is a lithium-ion battery sealed in a soft pouch. With age, heat and overcharging, the liquid inside (the electrolyte) slowly breaks down — and makes gas. Swollen battery? What should you do?

Question 13

Why does your phone screen turn off at your ear?

Accepted Answer

A proximity sensor beside the earpiece shines invisible infrared light; when your ear reflects it back, the phone turns the screen off so your cheek can't tap it. Up at the top, next to the speaker, hides a tiny proximity sensor. It shines invisible infrared (IR) light in short pulses, again and again. Nothing near? The light flies away → screen stays on. So your cheek can't press MUTE or hang up by accident — and it saves battery. (Tip: a phone camera can sometimes see that IR light!).

Question 14

How does a smoke alarm smell smoke?

Accepted Answer

A photoelectric alarm shines a light inside a dark chamber; smoke scatters it onto a sensor → beep (ionization alarms instead notice smoke slowing a tiny current). Most home alarms are PHOTOELECTRIC: inside is a dark little chamber. A tiny infrared light shines across it — but AWAY from the light sensor, so normally the sensor sees nothing. When smoke drifts in, the tiny smoke particles bounce some of that light sideways onto the sensor → BEEP!

Question 15

Why do you see a spark when you pull a plug out?

Accepted Answer

The current tries to keep flowing (inductance) and jumps the tiny air gap as an arc. THE TINY GAP: current is flowing through the plug, and it doesn't want to stop. As the pin slides out, the last tiny contact point gets very hot, and the current keeps going for a moment through the hot air in the gap — that's the spark (an arc). COILS = BIGGER SPARK: motors, fans, vacuum cleaners and many chargers have coils inside. A coil stores energy in its magnetic field and fights any change in current, so it pushes harder — a bigger spark.

Question 16

How does your TV remote talk to the TV?

Accepted Answer

An infrared LED blinks codes on a ~38 kHz carrier; your phone camera can see it. INVISIBLE LIGHT: the little LED at the front flashes infrared light (about 940 nm) — your eyes can't see it. But your phone camera can! A CODE PER BUTTON: every button sends its own pattern — bursts of flashes with short and long gaps = 1s and 0s. Inside each burst the LED flashes about 38,000 times a second (38 kHz). THE TV'S EAR: the TV's receiver only listens to that 38 kHz beat, so steady light from lamps and the sun can't fool it.

Question 17

Why do power lines use such high voltage?

Accepted Answer

Same power at higher voltage = less current, and line loss = I² × R. WIRES WASTE HEAT: every wire has some resistance, so it turns some power into heat. That loss = current² × resistance — twice the current means 4× the heat! THE TRICK: power = volts × amps. Send the same 100 kW at 10× the voltage and you need only 1/10 of the current — and (1/10)² = 1/100 of the loss. THE GRID: transformers step it up to about 110,000–765,000 V for the long lines, then step it down for your home: 230 V · 50 Hz (India, UK, Europe) or 120 V · 60 Hz (USA, Canada).

Question 18

Why do transformers hum?

Accepted Answer

The iron core changes size slightly 100 times a second on 50 Hz mains (magnetostriction) → a 100 Hz hum. IT'S A MAGNET: inside is an iron core. AC in the coil turns it into a magnet — and flips it again and again (50 Hz in India, UK, Europe · 60 Hz in the USA, Canada). THE IRON STRETCHES: every time the iron is magnetised it gets a tiny bit longer, then shrinks back. It's called magnetostriction — only a few millionths of its length, but enough to shake the air.

Question 19

How does a metal detector find metal?

Accepted Answer

A coil makes a changing magnetic field, metal answers with eddy currents that a second coil picks up. THE SENDER COIL: the round head has a coil of wire carrying alternating current. That makes a magnetic field that reaches into the ground — and flips direction thousands of times a second. INSIDE THE METAL: a changing magnetic field makes currents swirl inside any metal (they're called eddy currents). Those swirling currents make a small magnetic field of their own.

Question 20

Why does your phone battery die faster in the cold?

Accepted Answer

The lithium-ion chemistry slows down, internal resistance rises, the voltage sags. INSIDE THE BATTERY: lithium ions carry the charge from one side to the other. In the cold the liquid inside gets thicker and the chemistry slows down — the ions crawl, like honey. THE VOLTAGE DROPS: a cold battery can't push enough current. When you open the camera or an app, the voltage dips below the phone's safety cut-off… and it shuts down, even at 30 %!

Question 21

Why do LED bulbs last so much longer than old bulbs?

Accepted Answer

No thin filament burning at ~2500 °C; LEDs run cool and fade slowly (15,000–25,000 h vs ~1000 h). THE OLD BULB: it makes light by heating a thin tungsten wire to about 2,500 °C (4,500 °F). At that heat the metal slowly boils off, the wire gets a thin spot… and one day it snaps. THE LED: there's no hot wire at all. A tiny chip turns electricity straight into light. THE HOURS: a good LED bulb is rated for up to 25,000 hours — about 25× longer. At 3 hours a day that's around 20 years!

Question 22

How does a microwave heat food?

Accepted Answer

2.45 GHz waves twist water molecules back and forth billions of times a second → friction heat. THE MAGNETRON: a part inside the oven makes microwaves at 2.45 GHz (each wave is about 12 cm long). The metal walls bounce them around, and the mesh in the door keeps them inside. THE WATER: a water molecule has a minus end (oxygen) and a plus end (hydrogen). The microwaves' field flips direction billions of times a second, and the water keeps twisting to follow it.

Question 23

Why does your phone get hot while charging?

Accepted Answer

The charging chip and the battery's internal resistance turn some energy into heat (I²R); fast charging = more current = more heat. NO CHARGER IS PERFECT: the charging chip in your phone turns most of the power into stored energy, but a little of it becomes heat. THE BATTERY ADDS MORE: every battery has a tiny resistance inside. Heat = I² × R, so double the current gives FOUR times the heat. FAST = WARM: fast charging pushes more current, so it runs warmer. Too hot?

Question 24

Why don't birds get shocked on power lines?

Accepted Answer

Both feet on one wire = no voltage difference across the bird → no current. SAME WIRE: current only flows when there is a voltage DIFFERENCE. Both of the bird's feet sit on the same wire, so they are at the same voltage. EASY PATH: the copper between its feet has a tiny resistance, the bird a far higher one. So the current simply stays in the wire and almost nothing goes through the bird. TWO WIRES = ZAP: if a big bird touches a second wire (or a pole) with a wing, there are thousands of volts across its body and current flows through it. That's why large birds sometimes get hurt on power lines.

Question 25

How does an LED make light?

Accepted Answer

Electrons fall from a higher energy level to a lower one at the junction and give off the difference as light; the material sets the colour. Inside the tiny chip: two layers. N has extra electrons, P has "holes" (missing electrons).

Question 26

How does a fridge make cold with electricity?

Accepted Answer

A compressor squeezes a refrigerant gas; it evaporates inside the fridge and soaks up heat, then dumps that heat out of the coils at the back. Cold just means less heat — so a fridge pumps the heat out of the box. An electric compressor squeezes a special gas (the refrigerant) — squeezed gas gets hot.

Question 27

How do Bluetooth earbuds connect to your phone?

Accepted Answer

Bluetooth is a tiny 2.4 GHz radio: the phone compresses the song into small packets that hop between 79 channels about 1,600 times a second, and each bud turns them back into sound. Bluetooth = a tiny radio at 2.4 GHz (the same band as Wi-Fi). Your phone squeezes (compresses) the song into small packets.

Question 28

What is 5G, really?

Accepted Answer

Radio like 4G, but with wider channels, higher frequencies and many small antennas — more data at once, shorter range per mast. 5G is still radio waves — just like 4G. It's the 5th generation of mobile networks.

Question 29

How does a battery store electricity?

Accepted Answer

It stores chemical energy: charging pushes lithium ions to one side; using it lets them flow back while electrons run through your device. Inside a lithium-ion battery: two layers (graphite + metal oxide) with a thin wall between them. Charging pushes tiny lithium ions through the wall into one side.

Question 30

How does a phone camera turn light into a photo?

Accepted Answer

Millions of tiny light sensors (pixels) count the light that hits them; a grid of red, green and blue filters on top gives the colours. The lens squeezes the light onto a tiny chip — the image sensor. The chip holds millions of pixels (a 12 MP camera ≈ 12 million).

Question 31

Why do electric cars accelerate so fast?

Accepted Answer

An electric motor gives full twisting force (torque) from zero speed, with no gearbox to shift. A petrol engine is weak at low revs — it has to rev up to a few thousand RPM to give its best pull (torque). An electric motor gives its FULL twist from zero speed — the moment you press the pedal.

Question 32

How does a QR code hold a link?

Accepted Answer

Black and white squares are bits; built-in error correction lets the code still work with up to about 30 % of it damaged. Each tiny square is a bit: dark = 1, light = 0. Your link becomes letters, letters become bits (8 per letter: 'e' = 01100101), bits become squares.

Question 33

What is a semiconductor, really?

Accepted Answer

A material between a conductor and an insulator; adding a tiny bit of another element (doping) controls how it conducts. Copper: electrons flow freely (a conductor). Glass: electrons are held tight (an insulator). Add a pinch of phosphorus — about 1 atom in a million — and it gets a spare electron to move. It conducts over a MILLION times better!

Question 34

How does internet travel through glass?

Accepted Answer

Fibre optics: light pulses bounce along a glass thread (total internal reflection) at about two-thirds of light speed. Inside a fibre-optic cable: a glass thread about as thin as a hair. A laser blinks: light ON = 1, light OFF = 0. How fast? About 200,000 km per second — two-thirds of the speed of light.

Question 35

How does a speaker turn electricity into sound?

Accepted Answer

A speaker = magnet + coil + cone: current makes the coil a magnet, the flipping (AC) current pushes and pulls it, and the cone squeezes the air into sound waves (note A = 440 a second). Inside every speaker: a magnet , a coil of wire and a light paper cone. Current in the coil turns it into a magnet too. For the note A, the cone moves 440 times a second (440 Hz)! The cone squeezes the air into waves — and your ear hears them.

Question 36

How does a CPU do billions of things a second?

Accepted Answer

A clock ticks billions of times a second (GHz); on every tick the transistors take one tiny step. Inside the chip, a tiny clock ticks 3 billion times a second — that's 3 GHz. On every tick, tiny switches (transistors) flip and the CPU takes one small step: Fetch an instruction. One tick is SO short (0.33 billionths of a second) that light only travels about 10 cm (4 in)! And a phone chip has about 8 cores, all working at the same time.

Question 37

How does a solar panel turn light into electricity?

Accepted Answer

Light knocks electrons loose at the P-N junction inside the silicon; the junction pushes them one way = a current. Each solar cell is two layers of silicon: N-type on top, P-type below. Where they meet (the P-N junction) there's a built-in push — an electric field. Light hits the cell and knocks electrons loose. The push sends them one way: up to the top layer. Connect a wire: the electrons flow out of the top, through your lamp, and back in at the bottom. That's a current!

Question 38

How does your phone remember things with the power off?

Accepted Answer

Flash memory traps electrons in a tiny insulated cell; trapped = 0, empty = 1, and they stay for years without power. FLASH MEMORY: your phone's storage is billions of tiny cells. Each one is like a little box with walls of glass (silicon dioxide — the same stuff glass is made of). SAVING A BIT: a push of voltage forces electrons through the thin glass wall into the box. When the push stops, they're trapped inside! READING IT: a box with trapped electrons means 0, an empty box means 1. The glass walls hold the electrons for years — no power needed.

Question 39

How does Wi-Fi send a video through the air?

Accepted Answer

Radio waves at 2.4 / 5 GHz; changing the wave's strength and timing (phase) encodes the 1s and 0s of your video. RADIO WAVES: your router makes radio waves at 2.4 GHz or 5 GHz — that's 2.4 or 5 BILLION wiggles every second. CHANGES = BITS: it keeps changing each wave's height and timing. Every tiny change carries a few 1s and 0s (real Wi-Fi packs up to 10–12 bits into each change). BACK INTO BITS: your phone reads those changes back into bits — about 5 million every second for HD video (around 20 million for 4K). That's your video!

Question 40

How does GPS know where you are?

Accepted Answer

Your phone times signals from 4+ satellites; distance = time × light speed, and the satellite clocks are corrected for relativity (about 38 microseconds a day). TIME SIGNALS: GPS satellites about 20,000 km up keep sending the exact time. Your phone times how long each signal takes to arrive — about 0.07 seconds. DISTANCE: time × light speed = distance (0.07 s × 300,000 km/s ≈ 20,000 km). One distance puts you on a big sphere, three distances pin you to one spot — and a fourth satellite fixes your phone's own clock.

Question 41

How does a computer think with just ON and OFF?

Accepted Answer

Billions of transistor switches form logic gates; gates add binary numbers, and everything a computer does is built from that. TINY SWITCHES: inside every chip are billions of tiny switches called transistors. ON means 1, OFF means 0. GATES: join two switches in a row and you get a logic gate. Only when A AND B are both on does the output turn on. MATHS: gates can add numbers in ones and zeros: 1 + 1 = 10 — that's "two" in binary. Billions of gates doing this, billions of times a second, run your apps, photos and games.

Question 42

What is electricity, really?

Accepted Answer

Electrons in a wire crawl slower than a snail (a fraction of a millimetre per second), but the push travels almost at light speed, so the lamp lights instantly. WIRES ARE FULL: a copper wire is already packed with tiny electrons. Electricity is all of them moving together. THEY CRAWL: those electrons are SLOW — slower than a snail! With 1 amp in a 1 mm² copper wire they drift about 0.07 mm per second. SO WHY IS THE LIGHT INSTANT? Because the PUSH travels at nearly the speed of light — like a tube full of marbles: push one in at one end and one pops out of the other end at once.

Question 43

Is it true that more megapixels always means better photos?

Accepted Answer

Mostly myth. Sensor size, lens and processing matter more; tiny pixels collect less light. A megapixel is just 1 million dots (pixels) in the photo. 12 MP (about 4000 × 3000) is ALREADY more dots than a 4K screen shows (3840 × 2160 ≈ 8.3 MP).

Question 44

Is it true that unplugging a phone at 100 % right away is a must?

Accepted Answer

Mostly myth. Modern phones stop charging at 100 % and top up only a little; optimised / adaptive charging holds at ~80 % overnight to reduce wear. At 100 %, a charging chip inside the phone STOPS the charging — it can't overcharge. On the charger it only tops up a tiny bit now and then (99 → 100 %).

Question 45

Is it true that dark mode saves battery on every phone?

Accepted Answer

Half true. On OLED screens black pixels are switched off, so dark mode saves power; on LCD screens the backlight stays on, so it saves almost nothing. OLED screens: every pixel makes its own light, so black pixels switch OFF — dark mode helps. LCD screens: one backlight shines behind everything and stays on — dark mode saves almost nothing.

Question 46

Is it true that full signal bars mean fast internet?

Accepted Answer

Myth. Bars show signal strength, not speed; a busy mast or slow network can be slow with full bars. The bars only show how STRONG the signal is — how well your phone hears the tower. They don't show how busy that tower is.

Question 47

Is it true that leaving Bluetooth on drains your battery?

Accepted Answer

Mostly myth. Modern Bluetooth Low Energy uses very little power when idle; the screen and mobile signal use far more. Old Bluetooth was hungry. Today's Bluetooth Low Energy sips power: when idle it sleeps and only wakes for tiny blinks.

Question 48

Is it true that charging from a laptop USB port damages your phone?

Accepted Answer

Myth. A laptop port just gives fewer watts, so it charges slower; the phone only takes what it can handle. Your phone only takes what it can handle — the port can't "push" too much into it. An old USB port (USB 2.0) gives just 5 V × 0.5 A = 2.5 W, so it charges SLOWLY… …but it's perfectly safe.

Question 49

Is it true that a bigger-watt charger will damage your phone?

Accepted Answer

Myth. The phone and charger agree on the power (USB PD); the phone only takes what it can handle, so a certified 65 W charger is safe for a 20 W phone. The phone and the charger talk first (USB Power Delivery): the charger lists what it can do — 5, 9, 15, 20 V… The phone asks for what it can take: "20 W, please!" → the charger agrees: 9 V × 2.22 A. The phone PULLS the power — the charger never pushes more.

Question 50

Is it true that putting a dead battery in the freezer brings it back to life?

Accepted Answer

Myth. Cold slows the chemistry instead; the old trick only helped some ancient NiMH cells a little, and the water that condenses can damage the battery. MYTH! Cold doesn't recharge anything — it just slows the chemistry.

Question 51

Is it true that airplane mode makes your phone charge faster?

Accepted Answer

Mostly fact (a little). With the radios off the phone uses less power, so a bit more of the charger's power goes into the battery — the charger's watts still matter most. Your charger's power splits two ways: into the battery AND into running the phone. Even with the screen off, Wi-Fi, mobile data and Bluetooth keep searching and sending. How much faster? Usually just a few minutes (a bit more if your signal is weak).

Question 52

Is it true that a bigger power bank charges your phone faster?

Accepted Answer

Myth. mAh is only the tank size; charging speed is set by the watts (volts × amps) the power bank and cable can deliver. mAh is only the size of the tank: how much energy it holds. Speed comes from WATTS: volts × amps (5 V × 2 A = 10 W, 9 V × 2.2 A ≈ 20 W). Check the W number on the label. Use a good cable (and a phone that supports fast charging).

Question 53

Is it true that switching a light on uses more power than leaving it on?

Accepted Answer

Myth. An LED bulb's switch-on surge lasts a few thousandths of a second and uses less energy than one second of light (under 1 J vs 9 J for a 9 W bulb); switch LEDs off whenever you leave. When you flip the switch, an LED bulb takes a tiny surge — but it lasts only a few thousandths of a second (a blink is about 0.3 s!). That surge uses less energy than ONE second of light: under 1 J vs about 9 J for a 9 W LED bulb. Verdict: MYTH. With LEDs, switch them off every time you leave the room.

Question 54

Is it true that a charger left in the socket wastes lots of power?

Accepted Answer

Mostly myth. A modern phone charger with nothing attached uses under 0.1 W (well under 1 kWh a year); unplug old or cheap ones for safety, not savings. We measured it with a plug-in power meter, no phone attached: A modern phone charger uses under 0.1 W. (The rules in the EU and USA say 0.1 W max.). In a whole year: 0.1 W × 8,760 hours ≈ 0.88 kWh → about $0.15. So: MOSTLY MYTH. BUT: old chargers used more, and cheap uncertified ones can get hot. Unplug those — for safety, not savings.

Question 55

Is it true that a bigger battery (more mAh) always means a longer-lasting phone?

Accepted Answer

Mostly myth. The screen, the chip and the software decide how fast the energy is used; mAh is only the tank size. Battery life = the energy stored ÷ how fast the phone uses it. Phone A: 5,000 mAh (19.3 Wh), big bright screen + hungry chip → uses about 2.4 W → dead in about 8 hours. Phone B: 4,000 mAh (15.4 Wh), efficient screen + chip → uses about 1.6 W → lasts about 9.6 hours. Tip: compare real battery-life tests, not just mAh.

Question 56

Is it true that closing apps saves battery?

Accepted Answer

Mostly myth. Reopening apps from scratch can use more power than keeping them paused. IN THE BACKGROUND: your phone freezes (pauses) apps you're not using. A paused app uses almost no power. CLOSE IT: next time you open it, it has to start from scratch — load everything from storage again. That loading can use MORE power than just waking up a paused app. THE REAL DRAIN: a bright screen, weak signal, and apps that really keep running in the background, like maps with GPS. Your phone's Battery settings show which apps use the most.

Question 57

Is it true that using your phone while it charges is dangerous?

Accepted Answer

Myth with a good charger and cable; the real danger is cheap fake chargers. THE SAFE PART: with a good charger and cable, it's safe — phones are built for it. A charge controller inside watches the current and the temperature. WHAT REALLY HAPPENS: the phone gets a bit warmer and charges slower, because the charger's power is shared — some charges the battery, some runs the screen and chip. That's normal. THE REAL DANGER: cheap fake chargers, broken or frayed cables, and charging under your pillow (the heat can't escape).

Question 58

Is it true that LED bulbs don't get hot?

Accepted Answer

Myth. The driver and heatsink get warm, just far cooler than an old bulb. MYTH! WHERE THE POWER GOES: a good LED bulb turns only about 30–45 % of its power into light. Over half still becomes heat — mostly in the base, where the driver and the heatsink are. HOW HOT: the base of an LED bulb can reach about 60 °C (140 °F) — too hot to hold! An old 60 W bulb's glass runs even hotter: over 120 °C (250 °F). HEAT KILLS LEDs: the hotter they run, the shorter they live. Use open fittings — or, for closed glass fittings, buy bulbs marked "suitable for enclosed fixtures".

Question 59

Is it true that rubber slippers make you 100 % safe from shock?

Accepted Answer

Myth. Wet or worn soles conduct, and touching two wires bypasses your feet. THE SOLE: dry, thick rubber does block current — a little. But wet, dirty or worn soles let it through, and most slippers are not rated for electrical work. HAND TO HAND: touch live with one hand and neutral with the other, and the current goes hand → chest → hand. Your feet are not even in that path — so the slippers do nothing. THE REAL PROTECTION: always switch off the breaker first, check the wire is dead with a tester — or call an electrician.

Question 60

Is it true that it's the voltage that kills, not the current?

Accepted Answer

Half true. Current through the body does the harm, but voltage is what pushes it through your skin. CURRENT DOES THE HARM: it's the current flowing through your body that hurts you. About 1 mA you can feel, about 10 mA you can't let go, about 30 mA makes breathing hard — and about 100 mA (a tenth of an amp) can stop a heart. BUT VOLTAGE IS THE PUSH: current = voltage ÷ resistance, and your skin is the resistance. A 12 V car battery can give hundreds of amps to a starter motor, but through dry skin (about 100,000 Ω) it pushes only about 0.12 mA — you can't even feel it.

Question 61

Is it true that a 20,000 mAh power bank charges a 5,000 mAh phone 4 times?

Accepted Answer

Myth. mAh is at 3.7 V and losses are ~30–40 % → about 2.5 times. MYTH! You'll get about 2.5 full charges. WHERE IT GOES: the power bank boosts its 3.7 V cells up to 5 V, the cable has resistance, and your phone's charging chip has losses too. Together, about a third of the energy turns into heat. THE REAL MATH: 20,000 mAh × 3.7 V = 74 Wh. 74 Wh − ⅓ heat ≈ 48 Wh. Rule of thumb: expect about two-thirds of the number on the box — and check the Wh on the label.

Question 62

Myth or fact: "Drain your battery to 0 % before charging"?

Accepted Answer

Myth for lithium-ion: deep discharges age it faster; 20–80 % is kindest. MYTH! That rule was for old nickel (Ni-Cd) batteries from the 1990s. Your phone uses lithium-ion. It has no real memory effect, and draining it to 0 % stresses it and ages it faster. So charge whenever you like — short top-ups are fine. Around 20 %–80 % is the kindest range. (Fun fact: "0 %" isn't truly empty — phones keep a small reserve to protect the battery.).

Question 63

Is it true that a TV on standby uses no power?

Accepted Answer

Myth. Standby still uses about 0.5–1 W, every hour of the year. MYTH! That little red light means the TV is still on: a tiny power supply stays awake, listening for your remote. A new TV uses about 0.5–1 W on standby — every hour, all year (24 h × 365 days = 8,760 hours). W × 8,760 h ≈ 9 kWh a year. Old set-top boxes can use 10 W or more on standby — about 10× as much (≈ 90 kWh a year). Tip: switch off at the wall (or use a power strip with a switch).

Question 64

Is it true that fast charging damages your battery?

Accepted Answer

Mostly myth. The phone controls the current and slows down near full; heat is the real enemy. MOSTLY MYTH! Your phone is in charge: it asks the charger for power (USB PD) and only takes what the battery can safely handle. Fast charging only happens when the battery is low (roughly 0–50 %). Near full, it slows right down to protect the battery. The real enemy is HEAT: use a good, certified charger. keep the phone cool — not on a pillow or under a blanket. avoid cheap no-name fast chargers.

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