2.16 AC & DC Current

Question 1

What is the national grid?

Answer 1

The national grid is a giant web of wires and transformers that covers the UK and connects power stations to consumers.

Question 2

What does the national grid do?

Answer 2

The national grid transfers energy electrically from power stations anywhere on the grid (the supply) to anywhere else on the grid where it’s needed (the demand) - e.g. homes and industry

Question 3

What are the two different types of current?

Answer 3

Alternating current (A.C) and Direct Current (D.C)

Question 4

What do transformers do and why?

Answer 4

Transformers are used to increase the generated electricity to have a very high potential difference (p.d) before it is transmitted through the network of the national grid. Transferring electrical power at a very high p.d. helps to reduce energy losses. The p.d. is then reduced by another transformer to a level that is safe for use before being supplied to homes and businesses.

Question 5

Alternating current (A.C)

Answer 5

In a.c. supplies the current is constantly changing direction. Alternating currents are produced by alternating voltages in which the positive and negative ends of the potential difference keep alternating.

Question 6

The UK domestic (mains) supply is an a.c. supply at around ____V. The frequency of the a.c. mains supply is 50 cycles per second or 50 Hz.

Answer 6

230

Question 7

What current do cells and batteries supply?

Answer 7

Direct current

Question 8

Direct current (d.c.)

Answer 8

Direct current is a current that is always flowing in the same direction. It’s created by a direct voltage. This voltage is usually smoothed out to provide a straight line on a graph of p.d. (voltage) against time.

Question 9

Direct current is supplied by:

Answer 9

Batteries & Cells

Question 10

The role of an oscilloscope is to:

Answer 10

Display how voltage changes with time