Question 1
A copper wire has a resistance of R at room temperature. If the temperature of the wire is increased, what will happen to its resistance?
A. Remains the same
B. Decreases
C. Increases
D. Becomes zero
Question 2
Which of the following materials has the highest resistivity at room temperature?
A. Silver
B. Copper
C. Iron
D. Rubber
Question 3
According to Ohm's law, if the voltage across a resistor is doubled, the current through it will:
A. Remain the same
B. Be halved
C. Be doubled
D. Be quadrupled
Question 4
A device consumes 60W of power when connected to a 240V supply. What is the resistance of the device?
A. 960 ohms
B. 480 ohms
C. 240 ohms
D. 120 ohms
Question 5
Which of the following is NOT a limitation of Ohm's law?
A. It does not apply to non-linear devices.
B. It does not apply at very high frequencies.
C. It does not apply to superconductors.
D. It does not apply to resistors.
Question 6
a) Define Ohm's law and state its mathematical expression. [2]
b) A resistor has a constant voltage of 12 V applied across it and carries a current of 3 A. Calculate its resistance using Ohm's law. [3]
Question 7
a) Explain the concept of resistivity and how it differs from resistance. [3]
b) A copper wire has a length of 2 m, a cross-sectional area of 1 x 10^-6 m^2, and a resistance of 0.1 ohms. Calculate its resistivity. [2]
Question 8
a) Define electric power and state its relation to voltage and current. [2]
b) A device operates on a voltage of 230 V and draws a current of 5 A. Calculate the power consumed by the device. [3]
Question 9
a) Describe the relationship between current, resistance, and the heat produced in a resistor. [3]
b) A 10-ohm resistor has a current of 2 A flowing through it. Calculate the heat produced in the resistor in 5 seconds. [3]
c) How would the heat produced change if the current is doubled? [2]
Question 10
a) Define resistivity and state its unit. [2]
b) A material has a resistance of 8 ohms when its length is 2 m and its cross-sectional area is 2 x 10^-6 m^2. Calculate its resistivity. [3]
c) How would the resistance change if the length of the material is halved while keeping the cross-sectional area constant? [2]