Electric & Atomic Currents
Ladies and gentlemen, for a crisp 100 points — tell me:
What’s the official name of the ‘push’ behind electric charge?
And now — double or nothing! Does our hero, the electric current, zip along as a.c. or d.c.… or BOTH?
The Coulomb (C), the unit of electric charge!
Both exist! a.c. changes direction, d.c. flows in one direction.
Start your engines! What simple formula lets you calculate how fast something zooms across the stage?
Here’s one for the quick thinkers:
Sound waves — do they shimmy sideways or shove forward?
1. speed=time/distance
2. They’re longitudinal — they shove forward!
Let’s warm up with a classic!
If something speeds up, it’s packing energy — kinetic energy!
But what delicious little formula tells us exactly how much?”
Pressure fans — this one’s for you!
When you squeeze force onto an area, what unit pops out the other side?”
KE=1/2 mv2
Pascal (Pa).
Step right up! Tell me — what happens around any wire the moment current starts flowing?
Which two quantities do you multiply to find work done — the kind of work even physicists approve of?
A magnetic field forms around the wire.
Work done = force × distance moved
I flash through space with no mass at all, Bounce off mirrors, make rainbows fall. I bend in water, but never break. What am I, whose path waves take?
We jitter and jostle in every place, Hotter and faster — we pick up the pace. We make solids expand, we make gases fly — What are we, always moving, never shy?
Light
Particles in random motion
Buzz in! What two particles chill inside the nucleus like VIP guests?
Your counters ready? This instrument clicks like a cricket when radiation visits… what is it called?
1. Protons and neutrons
A Geiger–Müller tube!
Up next — graph whisperers only!
The slope of a distance‑time graph gives you what juicy detail?
Break out your wave magic!
What’s the secret relationship between frequency and time period?
Speed.
T=1/f
Energy loves to move — but how?
Name one way heat slips from place to place like a ninja
Give me the iconic relationship linking mass, volume, and density.
Conduction, convection, or radiation
ρ=m/v
Magnets: classic troublemakers! Do they attract or repel each other — and which way around?
Your kettle is humming… Why does a current in a resistor heat things up?
Like poles repel; unlike poles attract
Electrical energy is transferred to thermal energy because electrons collide with ions, increasing temperature.
I shrink and shrink but never disappear,
Cut me in half year after year.
No scissors, no knife, yet I divide…
What am I, changing while atoms collide?
I push without touching, I pull without hands,
I shape every orbit in faraway lands.
Planets obey me, though none can see —
Who am I, ruling silently?
Half‑life of a radioactive substance
Gravity
Now for the boss‑level question…
A nucleus emits a beta particle — boom!
What happens to its atomic and mass numbers? Think quick!”
A radioactive isotope has a half‑life of 12 hours. Its initial activity is 640 Bq. What is its activity after 36 hours?
Atomic number ↑ by 1; mass number stays the same.
(Neutron → proton + beta.)
36 hours = 3 half‑lives
640 → 320 → 160 → 80 Bq
Deep‑thinking time! A falling object eventually stops speeding up.
Why does it chill out at terminal velocity?”
Hear the siren changing pitch as it zooms past?
That’s not your imagination — Describethis effect.
Weight remains constant; air resistance increases until it equals weight, resulting in zero net force.
Observed frequency increases when a source approaches and decreases when it moves away.
Explain why convection occurs in fluids.
Let’s dive deep — literally!
Explain how pressure changes as you go deeper into a liquid.
Warmer, less dense regions rise; cooler, denser regions sink, creating a convection current.
Pressure increases with depth due to the weight of the fluid above
Abracadabra! How do we turn plain iron into a useful electromagnet?
Why do metal surfaces get toasty faster than wooden ones in the sun? Show me you understand radiation!
Wrap a coil of wire around it and pass a current through the coil.
Shiny, light surfaces reflect radiation; dull, dark surfaces absorb it more effectively
I look like my brother, but we’re not the same; One shakes side‑to‑side, the other forward in lane. We both carry energy from here to afar —
Who are we, dancing under the wave star?
I move through metal but not through wood, I light up your home like a superhero should. You can’t see me travel, but lamps show I'm near — Who am I, flowing far and near?
Transverse and longitudinal waves
Electric current
1. Explain why gamma radiation is suitable for sterilising medical equipment.
2. Describe the difference between irradiation and contamination.
1. It is highly penetrating and kills microorganisms without heating the object.
2. Irradiation = deliberate exposure to radiation only.
Contamination = Accidental exposure radioactive particles on/in the material.
Turbo challenge! A car speeds from 10 m/s to 26 m/s in 4 seconds.
What’s its acceleration? Your four‑second countdown begins… now!”
Refraction detectives — assemble! Light hits glass at 30°. The refractive index is 1.5. What sneaky angle does the ray bend to inside?”
4 m/s2
19.5°
Heavy lifters, this one’s yours! Lift a 2 kg mass up 5 meters — how much gravitational treasure (energy) have you stored?
Into the deep!
Density = 1000 kg/m³, depth = 12 m.
Crunch the numbers: what’s the pressure difference?
98 J. (Accept 100 J with rounded g)
117,600 Pa
For 400 points — impress me! A conductor moves through a magnetic field. What magical effect appears?
Time to flex your energy skills! A 50 W bulb runs for 2 minutes. How much energy does it burn through?
A voltage is induced across the conductor
6000 J.
Push me too little, I swing no more; Push me just right, I balance the score. Force and distance make my key — What am I, turning physics easily?
I’m born when coils twist and magnets move fast. Increase the motion—I grow unsurpassed. AC loves me, DC does not. What phenomenon have you got?
A moment (turning effect)
Electromagnetic Induction
1. A heater draws 5 A from a 230 V supply. Calculate the energy transferred in 2 minutes.
Electric shock alert! Why does raising resistance make the current tiptoe instead of sprint?
1. E=IVt=5×230×120=138,000 J
(138 kJ).
2. Because current is directly proportional to voltage and inversely proportional to resistance (Ohm’s Law: I=V/R).
Elite physicists only! A runner blasts from rest to 8 m/s over 20 m.
Use the mighty v2=u2+2as to uncover the acceleration.
Wave wizardry time! A water wave slows down in the same medium — frequency drops. To keep speed constant, what must the wavelength do? Justify
a=1.6 m/s2
Wavelength decreases because v=fλ; if v is constant and f decreases,λ must also decrease.
For the big points — gas behavior!
Why does heating a gas at constant volume crank up its pressure like a pumped‑up athlete?
A gas at constant volume obeys p1/T1=p2/T2. If its pressure is 150 kPa at 300 K, find its pressure at 450 K.
Heating increases the average kinetic energy of molecules; they collide more frequently and forcefully with container walls, increasing pressure.
225 kPa.
Big brain time! A current‑carrying wire feels a force inside a magnetic field. Why? Tell me the physics magic behind it.
Here’s your boss‑level challenge:
Explain why a transformer can change voltage, but ONLY when alternating current is used.
Because moving charges experience a force when they move perpendicular to a magnetic field — the basis of the motor effect.
A changing current (a.c.) produces a changing magnetic field in the primary coil.
This varying magnetic flux induces a voltage in the secondary coil.
d.c. does not create a changing magnetic field, so no induction occurs.
I hit the wall though I never strike, I push with pressure just how you like. Heat me up and I punch even more — Who am I behind the container door?
I slip through lead as though it’s thin, Barely noticed when I’m in. Strong sources make me a danger revealed — What am I, the radiation that’s hardest to shield?
Gas pressure from particle collisions
Gamma radiation