A.C. Current

Question 1

What is an alternating current?

Answer 1

It is a current with direction that changes periodically.

Question 2

What is a direct current?

Answer 2

It is a current with one direction only.

Question 3

What is the root-mean-square value of an alternating current?

Answer 3

It is the value of a steady d.c. that will dissipate energy at the same average rate as the a.c. in a resistive load.

Question 4

What is a Transformer?

Answer 4

It is a device used to change the alternating voltage and current to a larger or smaller value.

Question 5

What is Rectification?

Answer 5

Rectification is the process of converting a.c. to d.c.

Question 6

What is the use of using a soft iron core?

Answer 6

To increase flux linkage and minimise leakage.

Question 7

What is the use of laminating the core?

Answer 7

To reduce energy loss due to heat by reducing induced/eddy current in the iron core.

Question 8

What is the use of eddy current for braking?

Answer 8

1. Used in providing braking or resistance without friction so that wear-and-tear is minimised.
2. The more rapidly a roller coaster is moving, the faster the brakes can slow it down.
3. They are not affected by weather and require little maintenance.

Question 9

Why would there be power loss in Transformer?

Answer 9

1. Heat dissipated in the iron core due to eddy current
2. Resistance of coils returns in in more heat dissipated
3. Some leakage of magnetic flux as not all magnetic flux produced by the primary coil may be connected to the secondary coil.