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Exam level4 past questions

Electrical Energy, Power, and Heating Effect

Calculate electrical energy, power dissipation, and understand the heating effect of current in various circuit configurations.

Why this shows up in the exam

You will solve NEET problems on power, energy, and heat produced in resistors.

How NEET tests this

Numerical · 6 Qs

Learn the idea

Electrical energy is the total work done by a current and equals power multiplied by the time for which the power is delivered; the key insight is that power in a resistor can be written as I²R or V²/R, linking heat directly to current or voltage.

🧠 Memory hook: Power is the price per second; energy is the total bill – multiply price (W) by seconds to get joules.

Get this one clearly and it pays off every single time it shows up in the paper. 🎯

Formulas & facts to keep ready

  • Energy (J) = Power (W) × Time (s)
  • Power (W) = Voltage (V) × Current (I)
  • Power (W) = I² × Resistance (Ω)
  • Power (W) = V² ÷ Resistance (Ω)
  • In a resistor the thermal energy developed = I²R t
  • Convert kW to W (×10³) and hours to seconds (×3600) before using the formula

How to approach it

  1. 1Read the question and decide whether it asks for energy, power or a ratio of heats
  2. 2Write the appropriate formula from the key ideas, keeping units in SI
  3. 3Substitute the given numerical values, converting kW→W and hour→second if needed
  4. 4Simplify; for ratio problems cancel common factors and use I²R or V²/R proportionality

Worked example — watch it click

The energy that will be ideally radiated by a 100 kW transmitter in 1 hour is:

  • ✅36 × 10⁷ J
  • B)36 × 10⁴ J
  • C)36 × 10⁵ J
  • D)1 × 10⁵ J

The concept behind this problem

The example checks that you can translate a power rating given in kilowatts and a time given in hours into the corresponding energy in joules using E = Pt, with correct unit conversion.

Step by step

  1. 1Energy = Power × Time = 100 kW × 1 hour = 100×10³ W × 3600 s = 3.6×10⁸ J = 36×10⁷ J.

Watch out

Treating 100 kW as 100 W or 1 hour as 60 seconds, which makes the answer three orders of magnitude too small.

Common slip-ups that cost marks

  • •Missing the factor 10³ when converting kW to W
  • •Using 1 hour = 60 s instead of 3600 s
  • •Applying series formulas to a parallel network or vice‑versa

🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.

Practise it

These are real questions from past NEET papers that test this exact idea.

Question 1 of 4NEET 2022

The energy that will be ideally radiated by a 100 kW transmitter in 1 hour is:

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