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
Core Practical: Construct electrical circuits to test series circuits using resistors and filament lamps METHOD
- Connect resistors or filament lamps in a single line.
- Measure current and voltage
- Observe how voltage divides and current remains the same in a series
Electrical energy is dissipated as what kind of energy?
- Thermal energy
Explain ways of reducing unwanted energy transfer through low resistance wires
- Use thicker wires.
- Shorten wire length.
- Choose high-conductivity materials.
Describe the advantages of the heating
effect of an electric current
- Efficient heating for various applications.
Describe the disadvantages of the heating
effect of an electric current
- Potential energy wastage without proper insulation.
- Safety hazards like fire and electric shock.
- Limited suitability for high-temperature applications
Explain how the power transfer in any circuit device is related to the potential difference across it and the current in it
P = I x V
Describe how energy is transferred from battery to the energy of motors and heating devices
Batteries convert chemical energy to electrical energy. In devices like toothbrushes and portable heaters.
Describe how energy is transferred from the a.c. mains to the energy of motors and heating devices
The a.c. mains supply electrical energy from the grid. Powers washing machines and heating elements in devices like ovens.
Direct Current (d.c.)
- Electric charge flows in one direction, like a straight line.
- Used in batteries and many electronic devices.
- Voltage stays the same
Alternating Current (a.c.)
- Electric charge direction alternates
- Used in homes and most appliances.
- Voltage goes up and down regularly.
What is the UK’s domestic supply and its info
- a.c.
- 50hz
- 230 V
Explain the function of the live mains input wire
- Carries electricity from the power source to the device.
Explain the function of the neutral mains input wire
- Completes the electrical circuit
Explain the function of an earth wire in ensuring safety
-It provides a path for electricity to escape, preventing fires
Explain the function of fuses or circuit
breakers in ensuring safety
- Inhibtis flow of electricity if current gets too high
- This prevents damage to other appliances
What is the voltage between live, neutral and earth main wires?
- Live Wire: Around 230 volts AC
- Neutral Wire: Close to zero voltage
- Earth Wire: Zero voltage
Explain the dangers of providing any connection between the live wire and earth
- Electric Shock Risk
- Fire Hazard
- Equipment Damage
- Electrical System Damage
Explain how the power ratings of home appliances relate to changes in their stored energy when they’re being used, using examples
- Higher ratings mean more energy consumption (e.g. microwave uses more energy than a toaster)
Core Practical: Construct electrical circuits to show relationship between voltage, current and resistance for a resistor and lamp VARIABLES
- Dependant: current
- Independent: voltage around
- Control: voltage in power supply and equipment
Core Practical: Construct electrical circuits to test series circuits using resistors and filament lamps VARIABLES
- Independent: Components used (e.g., resistors, filament lamps).
- Dependent: Circuit behaviour (e.g., brightness, current flow).
- Controlled: Voltage of power supply.
