Question

Read the following passage and answer the questions that follow:

Swati, a class 10 student, observes that when she passes close to the refrigerator in her kitchen, she feels the heat, although the things kept inside the refrigerator are cool.

(a) Describe the cause of heating in the above-mentioned case.    [1]

(b) A current I flows through a resistor of resistance R when the potential difference across it is V. Applying Ohm’s law, write the formula for amount of heat produced by the resistor in time t.    [1]

(c) (i) Write any two practical applications of heating effect of electric current.    [2]

OR

(c) (ii) Define the commercial unit of electric energy and express it in Joules (J).    [2]

Answer 1

(a) The refrigerator releases heat to the surroundings because its compressor and coils work continuously, converting electrical energy into heat (heating effect of current). Hence, heat is felt outside even though the inside remains cool.

(b) According to Ohm’s law and Joule’s law of heating:

H = V I t

(c) (i) Practical applications of the heating effect of electric current are:

• Electric iron
• Electric heater

OR

(c) (ii) The commercial unit of electric energy is kilowatt-hour (kWh).

1 kWh = 3.6 × 10⁶ J