Topic 10 - Electricity & Circuits Flashcards
Cell/Battery
- Provide circuit with voltage
Open/Closed Switch
- Allows current to flow
Fixed Resistor
- Limits flow of current
- Resistance cannot be changed
Variable Resistor
- Limits flow of current
- Resistance can be changed
LDR (Light Dependent Resistor)
- As light increases, resistance decreases
Thermistor
- As temperature increases, resistance decreases
Diode
- Forces current to flow in only one direction
LED (Light Emitting Diode)
- Forces current to flow in only one direction
- Emits light when current flows through
Motor
- Converts electrical to mechanical energy
Ammeter
- Measures current
Voltmeter
- Measures volts of a component
What are volts measured in?
- Joules per Coulomb (J/C)
What is an electric current?
- Rate of flow of charge
How does changing the resistance in a circuit change the current?
- As resistance increases, current decreases
If two resistors are in series, the net
resistance is increased. Why?
- Only one path for current, so the resistance adds up
If two resistors are in parallel, the net
resistance is increased. Why?
- Current can take multiple paths, so the resistance in each of them is less
Core Practical: Construct electrical circuits to show relationship between voltage, current and resistance for a resistor and lamp METHOD
- Set up the circuit with a fixed resistor.
- Adjust the voltage using a variable resistor.
- Record current readings and average them.
- Increase voltage gradually, repeating step 2-3
- Turn off between readings to prevent overheating.
- Record negative readings by switching terminals.
- Swap resistor with a filament lamp and repeat.
Explain how current varies with potential difference for filament lamps
Current increases with voltage, but not proportionally due to increasing resistance as the filament heats up.
Explain how current varies with potential difference for diodes
- Current flows in one direction with a small forward voltage drop.
Explain how current varies with voltage for fixed resistors
- As current increases, voltage increases
To explore resistance variations in Filament Lamps:
Create a circuit with a filament lamp and a variable resistor in series. Measure voltage and current.
Adjust the variable resistor to change voltage across the lamp. Record voltage and current readings to see how resistance changes
To explore resistance variations in Diodes:
Apply different voltages and record current to therefore record resistance
To explore resistance variations in Thermistors:
Change the temperature and record voltage, to therefore record resistance
To explore resistance variations in LDRs:
Change light intensity on the LDR and record voltage, to therefore record resistance