13 April 2015
6.4 Electrical Power and
Potential Difference.
Can you match these quantities to their units?
Current
Resistance
Power
Voltage
Charge
Ohms
Coulombs
Amps
Watts
Volts
13 April 2015
6.4 Electrical Power and
Potential Difference.
Answers
Current Amps
Resistance Ohms
Power Watts
Voltage Volts
Charge Coulombs
13 April 2015
6.4 Electrical Power and p.d.
Page 190 AQA Physics
• The Power of an electrical device is the
amount of energy it transfers every
second.
• The Power depends on the current and
potential difference (Voltage)
In the USA the Voltage is 110V. What would happen if you
plugged a UK device into this Voltage? What might happen if an
American plugged their device into the UK mains?
Power
• Power = Energy transferred (Joules, J)
(Watts, W)
Time (seconds, s)
E.g A light bulb uses 6000J of energy in 1 minute. How powerful is the bulb?
Power = ?
Energy = 6000J
Time = 1 minute = 60s
Power = 6000 / 60
Power = 100 Watts
Questions
1) An electric heater uses 3600000J in one hour. How much power does it
use?
2) A car engine is rated at 100kW. How much energy does it use in 1s, 1min
and 1 hour?
Page 190 Question a)
Electrical Power
Power
=
Watts, W
Current
x
Amperes, A
Potential Difference
Volts, V
E.g. What power is used by a 12V, 5A car bulb?
Power = 5A x 12V = 60 Watts
Answer Question b) p191. Then Question 2 in the summary questions
A pacemaker controls the beat of the heart. These contain explosive materials. If a
body is cremated the pacemaker will explode in the incinerator causing quite a bit of
damage and a really loud bang – not what you’d want at a funeral!