Mains electricity Flashcards
(39 cards)
Define electrical power.
Electrical power is defined as the rate at which energy is transferred or converted per unit of time, typically measured in watts (W).
What two quantities does electrical power depend upon?
The two quantities that electrical power depends on are the voltage and current of a device.
State the electrical power equation.
The electrical power equation is: P = I × V
Where:
P = power, measured in watts (W)
V = voltage, measured in volts (V)
I = current, measured in amperes (A)
True or False? The unit of power is joules (J).
False.
The unit of power is watts (W), where 1 watt is equivalent to 1 joule per second.
True or False? The unit watts (W) is the equivalent of joules per second (J/s).
True.
The unit watts (W) is the equivalent to joules per second (J/s).
Describe the purpose of an electrical fuse.
An electrical fuse is a safety device designed to cut off the flow of electricity to an appliance if the current becomes too large (due to a fault or surge).
What happens to the wire in a fuse when the current becomes too large?
If the current inside the wire becomes too large it heats up and melts.
Draw the electrical symbol for a fuse.
The electrical symbol for a fuse contains a horizontal rectangle with a horizontal line through the middle.
State the three fuse sizes.
The three fuse sizes are 3 A, 5 A and 13 A.
State the correct fuse size for an appliance that requires a current of 4.5 A.
The correct fuse size for an appliance that requires a current of 4.5 A is 5 A.
True or False? Power is the rate of doing work.
True.
Power is defined as the rate of doing work, or, the rate of energy transfer. It is measured in watts (W).
How is energy transferred related to work done in an electrical circuit?
Work done is equal to the energy transferred in an electrical circuit.
True or False? Work is done when energy is transferred by moving charges in a circuit.
True.
True or False? The energy supplied by the battery is equal to the energy transferred only to the wires of an electrical circuit with several components.
False.
The energy supplied by the battery is equal to the energy transferred to all the components in an electrical circuit.
What is the equation for calculating energy transfers in terms of current, potential difference and time?
The equation for calculating energy transfers in terms of current, potential difference and time is: E = I × V × t
Where:
E = energy transferred, measured in joules (J)
I = current, measured in amperes (A)
V = potential difference, measured in volts (V)
t = time, measured in seconds (s)
True or False? Mains electricity is potentially lethal.
True.
What is the definition of an electrical safety hazard?
An electrical safety hazard is a condition that poses a risk of electric shock or fire, such as damaged insulation or overheating cables.
What hazards do damp conditions pose to electrical circuits or appliances?
Hazards that damp conditions pose to electrical circuits or appliances are that the moisture can conduct electricity, causing a short circuit or posing an electrocution risk.
Define the term double insulation.
Double insulation is when an appliance has insulation around the wires and a non-metallic case, eliminating the need for an earth wire.
Define earthing.
Earthing is an electrical safety feature found in appliances with metal cases that provides a low resistance path to the earth to prevent electric shocks.
True or False? A fuse is an example of an electrical safety feature built into domestic appliances.
True.
What is the purpose of the earth wire in an electrical appliance?
The purpose of the earth wire in an electrical appliance is to provide a low-resistance path to the Earth for the current.
What is the role of circuit breakers in a house?
The role of circuit breakers in a house is to quickly shut off electricity if the current exceeds a certain value, protecting the electrical system.
Which materials are commonly used to insulate wires?
The materials commonly used to insulate wires are rubber and plastic.
