What is a series circuit?
A series circuit is one in which the same charge passes through all components, so the current through each component in the same.
What is a parallel circuit?
A circuit in which the charges is split between branches.
What two factors does the current in a circuit depend on?
- Potential Difference (V)
- Resistance (Ω)
What equation should be used to calculate potential difference if current and resistance are known? State the units for all 3 quantities.
V (V) = I (A) R (Ω)
What is an ‘Ohmic Conductor’? State the condition required.
- A conductor for which current and potential difference are directly
proportional - Resistance remains constant as current changes
- Temperature must be constant
List four components for which resistance is not constant as current changes.
- Lamps
- Diodes
- Thermistors
- LDRs
What happens to the resistance of a filament lamp as temperature increases? Why?
- Resistance increases
- Ions in metal have more energy, so vibrate more, causing more collisions with
electrons as they flow through the metal creating greater resistance
What is different about current flow through a diode?
- The current only flows in one direction
- Resistance is very high in the other direction, preventing current flow
State what happens to the resistance of a thermistor as temperatute increases.
The thermistor’s resistance decreases
Give two examples of why a thermistor may be used.
- Thermostat
- Freezer
What happens to the resistance of an LDR when Light intensity decreases?
The LDR’s resistance increases
Give an application for a LDR
- Street Lamps
- Night Lights
What are the two ways that a component can be connected in a circuit?
- Series
- Parallel
How does PD across two components vary when connected in series and parallel?
- Series: Total PD is shared between each component
- Parallel: PD across each component is the same
If two resistors are connected in parallel, what can be said about their total resistance?
Their total combined resistance is equal to the sum of the two individual resistances
If two resistors are connected in parallel, what can be said about their combined total resistance?
Their total resistance is less than the smallest of the two individual resistances
State two equations for the power of a circuit. Give units.
Power (W) = Current (A) x Voltage (V)
Power (W) = Current^2 (A) x Resistance (Ω)
State an equation linking energy transfered, power and time. Give units.
Energy (J) = Power (W) x Time (s)
How should a Voltmeter be connected in a circuit?
In parallel to the desired component
how should an ammeter be connected in a circuit?
In series in the direction of current flow
