Electricity 2 Flashcards
(33 cards)
What is power defined as in electrical terms?
The rate of transfer of energy
Power is measured in watts (W), where 1 watt is equivalent to 1 joule of work done per second.
What is the formula for power in electrical circuits?
P = VI
P represents power, V represents potential difference (voltage), and I represents current.
What does potential difference (V) represent?
The work done per coulomb
It is a measure of how much energy is transferred per unit charge.
How is current (I) defined?
The number of coulombs transferred per second
Current indicates the flow of electric charge.
What is the relationship between power, potential difference, and current?
Power is equal to potential difference multiplied by current
P = VI implies that power is the work done per second.
What is the equation relating voltage (V), current (I), and resistance (R)?
V = IR
This equation is derived from Ohm’s law.
What is the power output of a 24 W car headlamp connected to a 12 V battery in 2 hours?
172,800 J or 170 kJ
Calculated using W = P x t, where t is converted to seconds.
What is the total resistance of a 24 W lamp with a voltage of 12 V?
6.00 ohms
Calculated using R = V / I and P = VI.
What is the operating power of a robotic mutant Santa that converts 750 J of electrical energy into heat every second?
750 W
Power is equivalent to the energy converted per second.
What is the current flowing through a robotic Santa with a total resistance of 30 ohms and operating power of 750 W?
5.0 A
Current calculated using I = P / V, where V is derived from the resistance.
How is electrical energy calculated if you know the power?
Multiply power by time
W = P x t, ensuring time is in seconds.
What is the time taken by an electric kettle to boil water if it takes 4.5 minutes?
270 seconds
Time converted from minutes to seconds (4.5 × 60).
What energy does a kettle with a heating element transfer to water in 270 seconds at 230 V with a power output of 4 kW?
248,400 J or 250 kJ
Calculated using W = V x I x t.
True or False: Power is measured in joules.
False
Power is measured in watts (W), while energy is measured in joules (J).
Fill in the blank: The formula for calculating energy is W = _______.
P x t
Where W is energy, P is power, and t is time in seconds.
What is the significance of the equation P = VI?
It relates power to voltage and current
This equation is foundational in understanding electrical circuits.
What unit of electricity do electricity companies commonly use?
Kilowatt-hour (kWh)
A kilowatt-hour measures the power of an appliance multiplied by the length of time it is used.
What is the formula for calculating work done?
Work Done = Power * Time
Power is defined as the work done per second.
How many joules are in one kilowatt-hour?
1 kWh = 3.6 million joules
What is the relationship between watts and kilowatts?
1 kW = 1000 W
How many seconds are in one hour?
1 hour = 3600 seconds
How much energy does a 1500 W hairdryer use in 10 minutes in kWh?
0.25 kWh
Calculation: W = Pt = 1.5 kW × (10/60) hours = 0.25 kWh
What is the formula to calculate the cost of electricity?
Cost = No. of units × Price per unit
How much does it cost to use an 800 W microwave for 6 minutes at a rate of 16.1p per unit?
1.3p
Calculation: W = Pt = 0.8 kW × (6/60) hours = 0.08 kWh; Cost = 0.08 × 16.1 = 1.288p
