power Flashcards
What is the rate of doing work?
Power
Power is defined as the rate at which work is done.
What is the power formula for doing work?
Power = work / time
This formula expresses power in terms of work done over a period of time.
What does an Electromotive Force (EMF) do when applied to a circuit?
Push electrons
EMF is responsible for motivating electrons to flow in a circuit.
What are the two items that electrical power depends on?
- Voltage
- Current
Electrical power is directly related to both the voltage and the current in the circuit.
What is the formula for electrical power?
Power = current x voltage
This formula shows how electrical power is calculated using current and voltage.
What is the unit of electrical power?
Watts
The standard unit for measuring electrical power is watts.
How many watts make 1 horsepower?
746
1 horsepower is equivalent to 746 watts.
How can I find the rating, or power in watts, on domestic electrical equipment?
Market the equipment being used
The power rating is usually indicated on the equipment itself.
What is the current flowing through a 240 V, 60 W lamp using the power triangle?
0.25 A
Calculated using the formula: Current = Power / Voltage.
What are the two resistance values for an incandescent lamp?
- Cold resistance
- Hot resistance
These values differ based on the temperature of the filament.
How do we measure cold resistance?
Using the Ohms scale
Cold resistance is typically measured using an ohmmeter.
How do we calculate hot resistance?
Using the formula: R = V/I
Hot resistance is calculated based on voltage and current when the lamp is operating.
How do we quote the rating of motors that provide a mechanical output?
Horsepower
Motors are commonly rated in horsepower to indicate their mechanical output.
How many watts is a 2 horsepower motor?
1492 W
Calculated as: 2 x 746 = 1492 watts.
Which provides more light, a 100 W lamp or a 60 W lamp?
100 W lamp
The wattage indicates the amount of power consumed, which correlates with brightness.
What is the danger of passing a constant high current through a conductor?
Produce heat
Excessive current can generate significant heat, potentially causing damage.
How are resistors rated?
- Watts
- Ohms
Resistors are rated based on their power handling capacity and resistance value.
What effect do insulating materials have on electrical equipment?
Prevents heat loss
Insulation is crucial for maintaining efficiency and safety in electrical equipment.
How does a fuse work?
The metal in the fuse melts when the power consumed is too high
Fuses protect circuits by interrupting the flow of electricity when overloaded.
What does the fuse protect from damage?
Electrical equipment
Fuses safeguard equipment from excessive current that could cause failure.
Does the fuse protect the equipment being operated?
no
A fuse is designed to prevent damage to the equipment by breaking the circuit under fault conditions.
