Electricity Flashcards
What happens to the current, potential difference and the resistance in a series circuit?
The current is the same in all components
Total p.d is shared between all the components
Describe the current, potential difference and the resistance in a parallel circuit
Total current is the sum of each components current
P.d is the same across all components
Total resistance is less than the resistance value of the smallest individual resistor
Equation that involves current, resistance and power
Power = (current)∆ × resistance
Describe the resistance in a thermistor
Resistance varies with temperature
Resistance decreases as temperature increases
Describe the resistance in an LDR
Resistance varies with light intensity
Resistance decreases as light dcereases
What does the earth wire do?
Only carries current if there is a fault
What is an alternating current and give an example of what it is used in
Potential difference switches direction many times a second, current switches direction
What is a direct current and give an example of what it is used in
Potential difference remains in one direction, current flows the same direction
Cell or battery
What is the National Grid
It distributes electricity that is generated in power station in the UK
State and equation that involves energy transferred, time and power
Energy transferred = power × time
What is the frequency and voltage in the mains supply
50Hz and 230V
What are Random errors? Give an example
Random errors are differences from the true value which are larger AND smaller.
Anomalies
What are systematic errors? Give an example
Systematic errors are due to problems with method or instruments/ equipment
Change in temperature
Define Accuracy
Measured value is close to the true value
Define Precision
Repeated readings are close together
Using the equation E=P × t
Work out the energy transferred of an iron with a power of 3kW and is used for 240 seconds
E=3000 × 240
E=720000J
What is the efficiency equation?
Efficiency = useful power output ÷ total power input
What happens if the live wire comes loose in a plug?
The earth wire would take the charge and then if it starts to heat up the fuse would melt and stop the risk of electrocution
Describe the steps of how to measure whether the length or a wire affects the resistance
- Construct the circuit using an ammeter in series and a voltmeter in parallel with a resistor.
- Measure the voltage using the voltmeter
- Measure the current using the Ammeter
- Use the equation to calculate the resistance
- Change the length of the circuit and repeat the practical using steps 2-4 then record and compare the results
How many data readings do you need to plot a graph
At least 5
What is an ohmic resistor
It’s a resistor in which the current is directly proportional to the potential difference at a constant temperature
State the equation for resistance
Resistance = potential difference ÷ current
