Topic 10: Electricity And Circuits Flashcards
What are the 3 subatomic components that make up an atom?
- Electrons
- Protons
- Neutrons
Describe the structure of an atom?
- neutrons and protons in the nucleus
- electrons surrounding the nucleus in shells
In a closed circuit, what will there also be if there is a potential difference in the circuit?
Current
How is current defined?
As the rate of flow of charge (or electrons) around a circuit
What are the units of charge?
Coulombs, C
What are the 2 ways that a component can be connected in a circuit?
- Series (same loop)
- Parallel (adjacent loop)
What is voltage also known as?
Potential difference
How does the potential difference across 2 components vary when connected in series and parallel?
- In a series circuit the total P.D is shared between each component
- In a parallel circuit the P.D across each component is the same
If 2 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
If 2 resistors are connected in series, what can be said about their combined total resistance?
Their total combined resistance is equal to the sum of the 2 individual resistances
Where must a voltmeter be placed in a circuit?
In parallel with the component that is being measured
What can a volt also be described as?
Joule per coulomb
What is an electric current?
The rate or flow of charge
What can be said about the value of current at any point in a single closed loop?
Current is the same at all point in a closed loop
What 2 factors does the current in a circuit depend on?
- Potential difference (V)
- Resistance (R)
What is an ammeter and where must it be connected in a circuit?
An ammeter measures current, placed in series with the component it is required to measure
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 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 2 resistors in series?
The total resistance increases, it is equal to the sum of the 2 resistors
How is total resistance affected by 2 resistors in parallel?
The total resistance decreases, it is less than the resistance of the resistor with the lowest resistance
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
What are the 4 components for which resistance is not constant as current changes?
- Filament lamps
- Diodes
- Thermistors
- Light dependant resistors (LDRs)
What happens to the resistance of a filament lamp as the temperature increases? Why?
- Resistance increases
- Metal ions have more KE, so vibrate more, colliding more frequently with electrons as they flow through the metal
- This creates more resistance to current flow
What is different about current flow through a diode?
The current only flows in one direction, resistance is very high in the other direction
What happens to the resistance of a thermistor as temperature increases?
The thermistor’s resistance decreases
