Electricity and Circuits Flashcards
What three subatomic components make up an atom?
Protons
Neutrons
Electrons
Describe the structure of an atom
Protons and neutrons in the nucleus
Electrons surrounding the nucleus in shells
How is current defined
The rate of flow of electrons around a circuit
What two ways that a component can be connected in a circuit?
Series (same loop)
Parallel (adjacent loop)
Describe series circuits
Closed circuit
Current is the same everywhere
The p.d is shared between each component.
Describe parallel circuits
Branched circuit
Current splits into multiple paths
The p.d across each component is the same on each branch.
Where must the voltmeter be placed in a circuit?
In parallel with the component that is being measured.
What two factors does the current in a circuit depend on?
Potential difference
Resistance
What happens when current reaches a junction in a circuit?
Current is conserved; the total current remains the same and is split between the two branches.
How does resistance affect the current in a circuit?
As the total resistance of a circuit increases, the current flowing through the circuit decreases.
How can the current in a circuit be varied?
Using a variable resistor
How is total resistance affected by two resistors in a series circuit?
The total resistance increases; it is equal to the sum of two resistors.
How is total resistance affected by two resistors in a parallel circuit?
The total resistance decreases
What is an ohmic conductor?
- A conductor for which current and potential difference are directly proportional.
- Resistant remains constant whilst current changes.
- Temperature must be constant.
List four components in which resistance is not constant when current changes
- Filament lamps
- Diodes
- Thermistors
- Light dependent resistors (LDRs)
What happens to the resistance of a filament lamp as the temperature increases? Why? (3)
- Resistance increases
- Metal ions have more kinetic energy, so vibrate more, colliding more frequently with electrons as they flow through the metal.
- This creates more resistant to current flow.
What is different about current flow through a diode?
The current only flows in one direction.
Resistance is very high in other direction, preventing current flow.
State what happens to the resistance of a thermistor as temperature increases
The thermistor resistance decreases
Give two examples of when a thermistor may be used
- In a thermostat, to turn a heater on below a certain temperature.
- In a freezer, to turn on a cooler when temperature is too high.
State what happens to the resistance of an LDR as light intensity decreases
The resistance increases
Give an application for LDR
Street lamps - when light levels drop at night, resistance increases and the light gains sufficient current to turn on.
How do diodes work?
A diode only allows current to flow in one direction.
If current is flowing the right way, the resistance is large for small voltages, but then at higher voltages becomes very small.
What factors affect the energy transferred when charge flows through a component?
Amount of charge
The potential difference across the component
Define potential difference
The work done per unit charge
