Electrical Circuits Flashcards
What is current?
Current is the flow of electric charge
When will current only flow?
Will only flow around a complete (closed) circuit if there’s a potential difference
What is the unit for current?
ampere, A
In a series circuit, current has the … value current everywhere in circuit
In a series circuit, current has the same value current everywhere in circuit
What is potential difference (voltage)?
Is the driving force that pushes charge around
What is the unit for pd?
volt, V
What is resistance?
Anything in a circuit that slows the flow down
What is unit for resistance?
ohm, Ω
What happens to the current if you increase the resistance across a component?
Less current will flow through it (for a given potential difference across the component)
Draw the circuit diagram symbol for a cell

Draw the circuit diagram symbol for a battery

Draw the circuit diagram symbol for an open switch

Draw the circuit diagram symbol for a closed switch

Draw the circuit diagram symbol for a filament lamp/bulb

Draw the circuit diagram symbol for a fuse

Draw the circuit diagram symbol for a LED

Draw the circuit diagram symbol for a resistor

Draw the circuit diagram symbol for a variable resistor

Draw the circuit diagram symbol for an ammeter

Draw the circuit diagram symbol for a voltmeter

Draw the circuit diagram symbol for a diode

Draw the circuit diagram symbol for a LDR

Draw the circuit diagram symbol for a thermistor

What happens when a bigger current flows through a circuit
More charge passes around circuit
State the units for this equation Q = It (Charge = Current x Time)
Current = amperes (A)
Charge = coulombs (C)
Time = seconds (s)
What is Ohm’s Law?
Current through a resistor is proportional to the potential difference provided the temperature is constant
Does resistance of ohmic conductors (e.g. Wire or resistor) change with current?
No
Why does resistance of filament lamps change?
- When an electrical charge flows through a filament lamp, it transfers some energy to thermal energy store of filament (designed to heat up)
- As current increases, filament lamp heats up more and resistance increases
Why does resistance in diodes change?
They let current flow in one direction, but have a very high resistance if it’s reversed
Explain how increasing the temperature of component, increases the resistance?
Metal ions in wire will have more energy = more collisions with electrons = more resistance
In a LDR, as light intensity increases, resistance…
decreases
Draw a graph for a LDR

In a thermistor, as temperature increases, resistance…
decreases
Draw a graph for thermistor

In a series circuit, if you remove or disconnect one component, what will happen?
The circuit is broken and they all stop
What are series circuit good for?
To measure quantities and test components
In a series circuit, potential difference is…
shared
In a series circuit, current is…
the same
In a series circuit, total resistance…
is the sum of the resistance of each component
In a parallel circuit, potential difference is…
the same
In a parallel circuit, current is…
shared
At junctions, in a parallel circuit, current either…
splits or rejoins
Adding a resistor in parallel, has what effect on the total resistance?
It reduces the total resistance
Explain why if you add 2 resistors in parallel, their total resistance is less than resistance of the smallest of the 2 resistors
- In parallel, both resistors have same potential difference across them as the source
- ‘Pushing Force’ making current flow is the same as source of potential difference for each resistor that you add
- By adding another loop, current has more than one direction to go in
- Increasing total current that can flow around circuit. Using V = IR, an increase in current means a decrease in total resistance of circuit
How do you work out the total resistance of parallel circuit when there’s 2 resistors?

How do you work out the total resistance of parallel circuit when there’s more than 2 resistors?

What do you need to remember for resistance in a parallel circuit?
The combined resistance is less than that if either component