B - Electricity - Mains Electricity Flashcards
The formula for calculating electrical power is:
Power = Current x VoltageorP = IVWhere I – current in amps (A) V – voltage in volts (V)
A bulb operates at 230V. The current is 0.08A. Calculate the power of the bulb.
P = IVP = 230 x 0.08= 18.4 W (this would probably be an energy-saving bulb)
A hairdryer has a rating of 2kW. What current does it use?
P = IVI = P/VI = 2000/230I = 8.7A
A power supply produces a current of 0.5A and has a power output of 2.5W. Calculate its voltage output.
P = IVV = P/IV = 2.5/0.5V = 5V
A pair of curling tongs is rated at 1kW. Calculate the current it uses.
P = IVI = P/VI = 1000/230I = 4.35A
A current of 0.5A flows through a power supply producing 12V. Calculate the output power.
P = IVP = 12 x 0.5P = 6 W
Calculate the power of an electric can opener that uses 0.2 A.
P = IVP = 230 x 0.2P = 46 W
Two equations for calcultaing Energy
E = IVtWhereI – current in amps (A)V – voltage in volts (V)t – time of flow in seconds (s)E – energy used in joules (J)Notice that: P = IVSo we can replace the It in the equation above with: E = Pt
Names 5 Electrical Hazards
- Frayed Cables
- Long cables
- Damaged Plugs
- Water
- Metal Objects
What wire is connected to the metal casings of appliances?
Explain Why
The Earth wire
What size of fuse would you use for an appliance rated at 2.5 kW?
13 A
What size of fuse would you use for an appliance rated at 500W?
3 A
What does this symbol mean?
Double Insulated
When electricity flows in one direction only then the circuit is using
DC
Direct Current
When a circuit has a current flow that is constantly changing direction then the circuit is using
AC
alternating Current
