Ratio of thermal energy released in two resistors R and 3R connected in parallel in an electric circuit is :

Solution

Physics sir · 3 steps

In parallel the voltage is shared, so use P = V²/R: the smaller resistor heats more.

1. Same voltage. Resistors in parallel sit across the same two points, so both have the same potential difference V across them. They are on for the same time t too.
2. Pick the formula. With V common, write the heat as H = V²/Rt. Now only R changes between the two, and H goes as 1/R.

   H_R/H_(3R) = (V² t / R)/(V² t / 3R) = 3R/R = 3

3. So. The heat in R and 3R is in the ratio 3 : 1, which is option (d).

The idea to keep. Find what is common first. In parallel V is common, so heat goes as 1/R. In series I is common, so heat goes as R.

Answer from the NTA final answer key. Solution by PrepWiser.