Electricity and Circuits Flashcards
What is a Current?
The flow of electric charge around the circuit.
When will a current only flow through an electrical component?
If there is a potential difference across that component, and if the circuit is complete.
What is the unit for current??
Amps.
What is the potential difference?
Force driving the flow of electrons. Provided by cell/battery.
What is resistance?
Anything that slows down the flow of electrons.
The current flowing through a component depends on…
the potential difference across it and the resistance of the component.
What is current caused by in metals?
Flow of electrons.
What is the formula to work out charge if a current flows past a point in a circuit for a length of time.
Charge = Current X Time.
What is the energy transferred per coulomb of charge that passes between two points in an electrical circuit.
The potential difference.
How can you calculate the energy transferred?
Energy transferred = Charge moved X Potential difference.
The potential difference across an electrical component…
is the amount of energy transferred by that electrical component per unit charge passed.
One volt =
One joule per coulomb.
Potential difference =
Voltage.
What is the equation for potential difference?
Potential difference = Current X Resistance.
When an electrical charge flows through a component…
It has to do work against resistance. This causes an electrical transfer of energy.
When a current flows through a resistor, it heats up. Why is this?
Some of the energy transferred dissipates to the thermal energy stores of the component and the surroundings.
Explain why the resistor heats up in terms of electrons.
The electrons collide with the ions in the lattice that make up the resistor as they flow through it. This gives the ions energy, which causes them to vibrate and heat up.
The more the ions vibrate…
(In terms of resistor)
the harder it is for the electrons to get through the resistor. This means that for a given potential difference, the current decreases as the resistor heats up.
If the resistor gets too hot…
no current will be able to flow.
What does the standard test circuit contain?
An ammeter and voltmeter to measure current and potential difference.
A variable resistor to change the current through the circuit.
Why is an Ammeter and Voltmeter needed in the standard test circuit?
To measure current and potential difference.
Why is a Variable resistor needed in the standard test circuit?
To change the current through the circuit. Increasing the total resistance by increasing the variable resistor’s resistance lowers the current through the circuit.
What are IV graphs?
Graphs show how the current varies as you change the potential difference.
What type of IV graph do linear components have?
Straight line.
