## 1. SI unit of inductance is ?

1. Ohm
2. Coulomb
3. Henry

Memory: SI unit of inductance is farad.

## 2. Mutual inductance between two magnetically coupled coils depends on ?

1. Cross-sectional area of the core
2. Permeability of the core
3. Number of turns of the coils
4. All of the above

Memory: Mutual inductance between two coils defined by, M = N1 N2 μr μ0 a / l.

Where,

• N1 = Number of turns in coil one.
• N2 = Number of turns in coil two.
• μr = Relative permeability
• μ0 = permeability of free space.
• a = Area of cross-section.
• l = Length of the conductor.

## 3. An inductor stores energy in –

1. Electric field
2. Magnetic field
3. Electrostatic field
4. Free space

Memory: When current flows through an inductor, it stores energy in the magnetic field.

## 4. An inductor is a –

1. Passive element
2. Active element
3. Constant current source
4. Constant voltage source

Memory: An inductor is a passive element, because, it doesn’t create any energy by itself.

## 5. An inductor works on the principle of –

2. Ohm’s law
3. Lenz’s law
4. Coulomb’s law

Memory: An inductor works on the principle of faraday’s laws of electromagnetic induction.

## 6. An iron core coil its iron core is removed, so as to make it air core.

### What will be the inductance in this case ?

1. Less
2. More
3. Remain same
4. It is no longer an inductor

Memory: No information available.

## 7. In the above figure, inductors are connected in –

1. Series
2. Parallel
3. Series-Parallel
4. Parallel-Series

Memory: Here, inductors are connected in series.

## 8. An open coil has –

1. Infinite inductance and infinite resistance
2. Infinite resistance and zero inductance
3. Zero resistance and zero inductance
4. Infinite inductance and zero resistance

Memory: When a coil is open, it’s no longer an inductor but resistor.

## 9. Self inductance formula is shown above, the variable μr refers to –

1. Absolute permeability
2. Relative permeability
3. Permeability of free space
4. All of the above

Memory: Option B is correct.

## 10. Linkage flux per unit current is called ?

1. Resistance
2. Conductance
3. Capacitance
4. Inductance

Memory: Voltage across an inductor is directly proportional to the rate of change of current with time.

As shown in the below formula. ## 11. In the above figure, the two inductors L1 and L2 are connected in –

1. Parallel
2. Series
3. Parallel-Series
4. Series-Parallel

Memory: The two inductors are connected in parallel.

## 12. The Q factor of an inductor would be higher, if it is made of ?

1. Shorter wire
2. Longer wire
3. Thinner wire
4. Thicker wire

Memory: As Q factor of a coil is inversely proportional to the resistance of the wire.

Longer wire means higher resistance and lower Q-factor.

## 13. In the above figure, equivalent inductance between A and B is ?

1. 4H
2. 3H
3. 2H
4. 1H

Memory: Here, in the above figure, the equivalent inductance between points A and B is 3H.

As per the formula, (2*2/2+2)+1+1 = 3.

## 14. Two coils have self-inductances of 0.9H and 0.1H and a mutual inductance of 0.5H.

### The coefficient of coupling between the coils is ?

1. 5/4
2. 3/2
3. 5/3
4. 4/6

Memory: As per the formula, ## 15. The self inductance of a straight conductor is ?

1. High
2. Low
3. Zero
4. Infinite 