Name_____KEY______________________Period_________Date____________
Transformers
1.
What is the purpose of a transformer? Describe the components of a transformer.

2.
How do you step up voltage in a transformer?

3.
A transformer has two coils of wire on opposite sides of an iron core. The input
coils induce the voltage to the output coils on the other side to change the voltage
of the electricity.
To step voltage up, the secondary coil has to have more turns than the primary
coil.
You are planning a trip to Singapore and purchase a transformer. Curious, you open the
case and find that the primary coil has 46 turns and the secondary has 24 turns. Assuming
the secondary voltage is 120 volts, what is the standard household voltage in Singapore?
V1 N1
V2 N1 (120 V)(46 turns)
=
; V1 =
=
= 230 V
V2 N2
N2
24 turns
4.
A transformer has 20 turns on the secondary coil and 200 turns on the primary. What is
the secondary voltage if the primary voltage is 120 volts?
V1 N1
V1 N2 (120 V)(20 turns)
=
; V2 =
=
= 12 V
V2 N2
N1
200 turns
5.
A family from Finland, where standard household voltage is 220 volts, is planning a trip
to Japan. The transformer they need to use their appliances in Japan has an input coil with
250 turns and an output coil with 550 turns. What is the standard household voltage in
Japan?
V1 N1
V2 N1 (220 V)(250 turns)
=
; V1 =
=
= 100 V
V2 N2
N2
550 turns
6.
In England, standard household voltage is 240 volts. A transformer steps down voltage
from 240 volts to the 120 volts used by your hairdryer. If the primary coil has 50 turns,
how many turns does the secondary coil have?
V2 N1 (120 V)(50 turns)
V1 N1
=
; N2 =
=
= 25 turns
V2 N2
V1
240V
7.
When you plug in a cell phone, a transformer on the plug changes the outlet’s 120 volts
to the 6 volts needed by the battery. If the primary coil has 240 turns, how many turns
must the secondary coil have?
V2 N1 (6 V)(240 turns)
V1 N1
=
; N2 =
=
= 12 turns
V2 N2
V1
120V
8.
How many turns must the primary coil have if it steps down 13,800 volts to 120 volts
with 112 turns?
V1 N2 (13,800 V)(112 turns)
V1 N1
=
; N1 =
=
= 12880 turns
V2 N2
V2
120V