## 1. Ohm's law relates:

### Answer:

### Explanation:

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

## 2. The resistance of a wire is R. If its length is doubled without changing the volume, the new resistance will be:

### Answer:

### Explanation:

Resistance is directly proportional to length and inversely proportional to the area of cross-section. Doubling the length will double the resistance, but halving the area will quadruple the resistance.

## 3. The unit of electric current is:

### Answer:

### Explanation:

The SI unit of electric current is Ampere.

## 4. The resistivity of a material:

### Answer:

### Explanation:

For metals, resistivity generally increases with temperature, but for semiconductors, it decreases.

## 5. Kirchhoff's first law is based on the conservation of:

### Answer:

### Explanation:

Kirchhoff's first law, also known as the junction rule, states that the sum of currents entering a junction is equal to the sum of currents leaving the junction, which is based on the conservation of electric charge.

## 6. The reciprocal of resistance is:

### Answer:

### Explanation:

Conductance is the inverse of resistance and represents a material's ability to conduct electric current.

## 7. In a series circuit with resistors of unequal values:

### Answer:

### Explanation:

In a series circuit, the current remains constant across all components.

## 8. A device that converts electrical energy into mechanical energy is:

### Answer:

### Explanation:

A motor is a device that converts electrical energy into mechanical energy.

## 9. The power in an electrical circuit is given by:

### Answer:

### Explanation:

The power in an electrical circuit can be expressed as P = V^2/R or P = I^2R, depending on the known variables.

## 10. The drift velocity of electrons in a conductor is directly proportional to:

### Answer:

### Explanation:

Drift velocity is directly proportional to the electric field in the conductor, which is, in turn, proportional to the current.

## 11. Superconductors are materials:

### Answer:

### Explanation:

Superconductors are materials that exhibit zero resistance to the flow of electric current below a specific critical temperature.

## 12. The potential difference across a resistor carrying a current is 12V. If the power dissipated is 36W, what is the value of the current?

### Answer:

### Explanation:

Using the formula P = V*I, the current I = P/V = 36W/12V = 3A.

## 13. Which of the following materials has the highest resistivity?

### Answer:

### Explanation:

Rubber is an insulator and has much higher resistivity than metals like silver, copper, and iron.

## 14. A cell of emf 'E' and internal resistance 'r' is connected to an external resistance 'R'. The current in the circuit is maximum when:

### Answer:

### Explanation:

The current will be maximum (I = E/(r+R)) when the external resistance R is zero.

## 15. In the case of an ideal voltmeter, its resistance is:

### Answer:

### Explanation:

An ideal voltmeter has infinite resistance so that it does not draw any current from the circuit it's measuring.

## 16. The effect by which a current in one coil induces a current in a nearby coil is known as:

### Answer:

### Explanation:

Mutual induction is the phenomenon where a change in current in one coil induces a current in a nearby coil due to their mutual magnetic fields.

## 17. A wire of resistance 4 ohms is bent to form a circle. The resistance between any two points on the circle, diametrically opposite to each other is:

### Answer:

### Explanation:

When diametrically opposite points are connected, the current will take two equal paths. The effective resistance becomes half, i.e., 2 ohms.

## 18. A resistor is connected across a 60V source. If a current of 4A flows through the resistor, its value is:

### Answer:

### Explanation:

Using Ohm's law, V = IR. Therefore, R = V/I = 60V/4A = 15 ohms.

## 19. The color bands on a resistor represent:

### Answer:

### Explanation:

The color bands on a resistor typically indicate its resistance value, tolerance, and sometimes its power rating.

## 20. In an AC circuit, the current that leads or lags behind the voltage is due to:

### Answer:

### Explanation:

In an AC circuit, inductance causes the current to lag behind the voltage, while capacitance causes the current to lead the voltage.