Electricity Flashcards
What is the equation linking charge, current and time
Q = It
Q - charge, measured in C
I - current, measured in A
t - time, measured in s
What is the equation linking potential difference, energy and charge
V = E / Q
V - potential difference, measured in V
E - energy, measured in J
Q - charge, measured in C
What is the equation linking potential difference, current and resistance
V = IR
V - potential difference, measured in V
I - current, measured in A
R - resistance, measured in Ω (Ohms)
What is Ohms’ law
The current through a conductor is directly proportional to the voltage across it, provided its temperature is kept constant
Required practical : Investigate the factors that affect resistance
What is the method
Place a thin wire on a metre rule
Create a circuit using a cell, ammeter and voltmeter (parallel to cell)
Attach crocodile clips at 0 cm and 10 cm
Record reading on voltmeter and ammeter
Move the crocodile clip 10 cm away and record results until 90 cm away
Use the equation to find the resistance
What are the patterns and trends in the use of energy resources
During the Industrial Revolution fossil fuels were used a lot
Electricity became convenient in the 20th century
More energy is used in the early evening than overnight
The impact of fossil fuels caused science and society to develop renewable energy
Some developed countries use nuclear power
What is the equation linking power, current and resistance
P = I^2R
P - power, measured in W
I - current, measured in A
R - resistance, measured in Ω (Ohms)
What are the circuit rules
Current:
I1 = I2 = I3
Voltage:
V = V1 + V2
Resistance:
R = R1 + R2
What is the difference between an alternating and direct current
Alternate - current regularly changes direction
Direct - current flows in one direction
What is the mains electrical supply frequency and voltage
50 hertz
230 volts
What are the features of a plug
Cable grip - this holds the cable tightly in place so that wires do not become loose
Fuse - a canister with a thin wire that melts if the current gets too high
Neutral (blue) - completes the circuit (0 V). Left
Earth (yellow and green) - carries the alternating potential difference (230 V). Middle
Live (brown) - carries a current if there is a fault (0 V or 230 V). Right
What is the equation linking energy, power and time
E = Pt
E - energy, measured in J
P - power, measured in W
t - time, measured in s
What is the equation linking power, potential difference and current
P = IV
P - power, measured in W
I - current, measured in A
V - potential difference, measured in V
What do transformers do
Step up:
Voltage is increased from about 25,000 volts to 400,000 V causing the current to decrease. Less current means less energy is lost through heating the wire
Step down:
Reduces the voltage from the transmission voltage to the safer voltage of 230 V
