Practical electricity

Created by

Lux

Cards (41)

How is electrical energy calculated when charge flows through a potential difference?
Energy is calculated as E = QV
What is the alternative formula for electrical energy using current and time?
E = VIt
How can electrical energy also be expressed using resistance?
E = I²Rt
What is the equation for electrical energy in terms of voltage and time?
E = V²t
What are the equations for electrical energy?
E = Q V
E = I V t
E = I² R t
E = V² t
How much electrical energy does a torch bulb use if it operates at 1.5 V and 0.2 A for one minute?
18 J
How is electrical power defined in an electric circuit?
Power is the rate at which energy is released or transferred
What is the formula for calculating electrical power?
P = E/
How can power also be expressed in terms of voltage and current?
P = VI
What is the SI unit of power?
Watt (W)
What is another unit of power equivalent to a watt?
Joule per second (J/s)
What is the current in a bulb rated at 12 V and 600 W?
50 mA
What is the kilowatt hour (kWh) used for?
Unit of energy for calculating electricity bills
1 kWh is the energy converted by a 1 kW appliance used for 1 hour
How is energy consumed in kWh calculated for a 120 W television used for 300 minutes?
0.60 kWh
What is the cost of using a 3 kW heater for 4 hours at 16 ¢ per kWh?
192 ¢
How much does it cost to run a 100 W lamp for five hours each day for three weeks at $0.24 per unit?
$2.52
What are the components of a mains circuit?
Live wire
Neutral wire
Earth wire
What is the voltage of the live wire in a mains circuit?
Around 240 V
What is the purpose of the neutral wire in a mains circuit?
To provide a return path for current
What is the function of the earth wire?
To prevent the appliance from becoming live in case of a fault
What are the major hazards associated with electricity?
Risk of electric shock
Risk of fire
What can cause electric shock and fire hazards?
Damaged insulation
Overheating cables
Excess current from overloading
Damp conditions
What happens when insulation is damaged?
It can expose conducting wires, leading to electric shock or short circuits
What causes overheating of cables?
Unusually large current passing through conducting wires
What can result from overloaded power sockets?
Melting of insulation and electrical fire
How does dampness affect body resistance?
Dampness reduces body resistance, allowing high current to pass
What is the effect of touching a live wire at 240 V with dry skin?
Mild shock (2.4 mA)
What is the effect of touching a live wire at 240 V with wet skin?
Possibly fatal electrocution (240 mA)
What is the function of a fuse?
Prevents excessive current flow
Protects wires and appliances from overheating
Melts to open the circuit when current is too large
What happens when a fuse blows?
The circuit opens, preventing current flow
What is the purpose of the fuse rating?
Indicates the maximum current that can flow before it blows
What fuse rating should be chosen for an 800 W appliance on a 230 V supply?
5 A
What are the safety features in electrical systems?
Fuse
Switch
Circuit breaker
Earthing
Double insulation
What is the function of a switch in an electric circuit?
To break or complete the circuit
How does a circuit breaker work?
Switches off electrical supply when current exceeds rating
Uses an electromagnet to disconnect the circuit
Why must circuit breakers be connected to the live wire?
To cut off electrical supply when current exceeds rating
What are the advantages of using a circuit breaker over a fuse?
Can be reset
Turns off fire
Visible indication of tripped state
What is the purpose of the earth wire?
Protects users from electric shock
Connects metal casing of appliances to the ground
What happens when a live wire touches the metal casing without an earth wire?
Metal casing becomes live
User can get electrocuted if they touch it
How does an earth wire protect users?
Allows current to flow to the ground
Causes the fuse to blow, cutting off the live supply