current, resistance & potential difference

Define potential difference

The work done by a unit charge passing through a component

What is potential difference measured in

Volts

What's is the energy transferred between 2 points on a circuit

The potential difference between those two points in a circuit

Define current

The flow of electrical charge

What is current measured in

Amps

Define resistance

The opposition to current

E.g higher the resistance, lower the current

What is resistance measured in

Ohms

The resistance of a circuit can be increased by….

• adding resistors to it

• Every electrical component has a resistance, so the more you add the more resistance

The greater the resistance of the component the ___ the current for a given potential difference across the component

Lower

The lower the resistance of the component the ___ the current for a given potential difference across the component

Greater

What is the equation linking potential difference, current and resistance

Potential difference = current x resistance

V = IR

State Ohm’s law

The current through a conductor is directly proportional to the potential difference across it

What are ohmic conductors and give an example

Electrical conductors that obey Ohm’s law

• fixed resistors

• Wires

• Heating elements

What will the IV graph of an ohmic conductors look like

Straight line through the middle

What equation is Ohm’s law represented by

V = IR

Ohms law is only relevant at constant ___

Temperatures

What will the IV graph of a filament bulb look like and why

• As the current increases, the temperature of the filament in the lamp increases.

• The higher temperature causes the atoms in the metal to vibrate more.

• This increases resistance and therefore current increases more slowly.

What will the IV graph of a diode look like and why

A diode only allows current to flow in one direction, meaning in the reverse direction there is very high resistance

This means one side of the graph (reverse) has 0 current and potential difference

The other side (normal) has a sharp incraese in potential difference and current

What is the difference betweeen non-linear and linear components and how is it relevant to Ohms law

• linear components have a linear (straight line) graph and obey ohms law

• Non-linear components have a non-linear (Not straight line) graph and do not obey ohms law

Name 4 non-linear elements

• filament lamps

• Diodes & LEDs

• LDRs

• Thermistors