11 - Alternating currents

Question 1

Period (AC)

Answer 1

Time for one complete cycle of a.c.

Question 2

Frequency (AC)

Answer 2

Number of oscillations per unit time

Question 3

Peak value

Answer 3

Highest point on the graph

Question 4

Instantaneous current/ voltage

Answer 4

Current/ voltage at a particular instant

Question 5

root mean squared

Answer 5

Value of steady current or voltage that produces same power in a resistor as the a.c. or voltage.

Question 6

Transformer

Answer 6

Device used to decrease or increase the current or voltage of an alternative current

Question 7

Ideal transformer

Answer 7

no power loss in transformer

Question 8

Step-up transformer

Answer 8

primary coil has fewer turns than secondary coil, hence output voltage is greater (current decreases by same factor)

Question 9

Step-down transformer

Answer 9

primary coil has greater turns than secondary coil, hence output voltage is lower (current increases by same factor)

Question 10

Eddy currents

Answer 10

EMF induced when a metallic conductor moves in a metallic field which makes free electrons in a metal move, causing electric currents.