The resistance of a heating coil in a heating appliance operating at is .
[(a)] Which alloy is used to make heating coil of heating appliances?
[(b)] Calculate the amount of heat produced if electricity flows through this appliance for 5 minutes.
[(c)] If another appliance with a resistance less than is operated at the same voltage for 5 minutes, will the amount of heat produced increase or decrease? What is your justification?
Official Solution
Correct Option: (1)
(a) Alloy used Concept: Heating elements
Heating coils are made of materials with high resistivity and high melting point. Answer:(b) Heat produced Concept: Joule’s Law of Heating Step 1: Given data} Step 2: Substitute values} Step 3: Calculation} Conclusion (b):(c) Effect of decreasing resistance Step 1: Formula relation} Step 2: Observation}
At constant voltage and time:
Step 3: Conclusion}
If resistance decreases:
Final Answer (c):
02
PYQ 2026
medium
physicsID: kerala-s
(A) A heating appliance produces heat in 2 hours.
[(a)] What is the energy change in a heating appliance?
[(b)] Calculate the power of the appliance.
OR(B) An electric grinder with a power of is working.
[(a)] What is the energy change in this equipment?
[(b)] Calculate the work done by this grinder in 1 minute.
Official Solution
Correct Option: (1)
(A) Heating appliance (a) Energy change Concept:
A heating appliance converts:
Conclusion (a):(b) Power calculation Step 1: Given data} Step 2: Formula} Step 3: Calculation} Conclusion (b):(B) Electric grinder (a) Energy change Concept:
An electric grinder converts:
Conclusion (a):(b) Work done Step 1: Given data} Step 2: Formula} Step 3: Calculation} Conclusion (b):
03
PYQ 2026
medium
physicsID: kerala-s
A portion of electric circuit diagram of a household wiring is given.
[(a)] What does the part marked as “X” represent in the circuit?
[(b)] Draw a circuit diagram of a branch circuit which includes one three pin socket with switch.
Official Solution
Correct Option: (1)
(a) Identification of part “X” Concept: Household wiring components
In a typical household circuit, the sequence includes:
Step 1: Position of X}
The part “X” is placed after the main fuse and before ELCB. Step 2: Identify the component}
This component measures electrical energy consumed. Conclusion (a):(b) Circuit diagram of a branch circuit with three-pin socket and switch Concept: Three-pin socket connection
A three-pin socket has:
Live (L)
Neutral (N)
Earth (E)
Step 1: Connections}
Live wire passes through a switch to the socket.
Neutral wire directly connects to the socket.
Earth wire connects to the earth pin.
Step 2: Diagram} Step 3: Explanation}
Switch is always connected in live wire for safety.
Earth wire prevents electric shock.
Conclusion (b):
04
PYQ 2026
medium
physicsID: kerala-s
What does the term “Ohmic Heating” indicate?
1
Heating in a microwave oven
2
Heating in an induction cooker
3
Joule heating
4
Heating through radiation
Official Solution
Correct Option: (3)
Concept: Ohmic Heating
Ohmic heating refers to the heat produced when an electric current flows through a conductor due to its resistance. This phenomenon is governed by Joule’s law. Step 1: Joule’s Law of Heating}
The heat produced in a conductor is given by:
where:
= current
= resistance
= time
Step 2: Meaning of Ohmic Heating}
When current passes through a resistive material, electrical energy is converted into heat energy. This is called:
Step 3: Identify correct option}
Among the given options:
