JEE Main 2025 · PhysicsMultiple choiceSingle correctEasyCalculation

JEE Main 3 April 2025, Shift 2, Physics Q39

Question 39 of 75 in this shift, Physics question 14 of 25, Section A.

A motor operating on 100 V draws a current of 1 A. If the efficiency of the motor is 91.6%, then the loss of power in units of cal/s is

(1)6.2
(2)8.4
(3)4
(4)2Official answer

Official answer

Option 4

NTA final key.

Chapter: Current Electricity
Topic: Ohm's Law and Resistance
Idea tested: Joule Heating and Power

Same idea in other shifts

Asked 15× in all

4 Apr 2024, Shift 2 · Q42An electric bulb rated 50 $W$ - 200 $V$ is connected across a 100 $V$ supply. The power dissipation of the bulb is:EasySingle correct
8 Apr 2024, Shift 2 · Q41Water boils in an electric kettle in 20 minutes after being switched on. Using the same main supply, the length of the heating element…MediumSingle correct
8 Apr 2024, Shift 2 · Q56A heater is designed to operate with a power of 1000 W in a 100 V line. It is connected in combination with a resistance of $10\ \Omega$ …MediumNumerical valueHas a figure
31 Jan 2024, Shift 2 · Q41By what percentage will the illumination of the lamp decrease if the current drops by 20%?EasySingle correct
13 Apr 2023, Shift 1 · Q50Different combination of 3 resistors of equal resistance R are shown in the figures. The increasing order for power dissipation is: (A)…MediumDiagram basedHas a figure
13 Apr 2023, Shift 1 · Q60A potential $V_o$ is applied across a uniform wire of resistance R. The power dissipation is $P_1$ . The wire is then cut into two equal…EasyNumerical value
28 Jul 2022, Shift 2 · Q26An electrical bulb rated 220 V, 100 W, is connected in series with another bulb rated 220 V, 60 W. If the voltage across combination is…MediumNumerical value
25 Jun 2022, Shift 1 · Q57A resistor develops 300 J of thermal energy in 15 s, when a current of 2 A is passed through it. If the current increases to 3 A, the…EasyNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.