resistance

• the resistance of a component is the measure of how difficult it is for an electric current to pass through it
• the greater the resistance the smaller the current that flows as a charge must do work against the resistance which means energy is transferred
• current flowing through a component depends in the pd across it and resistance of the component
• pd is the driving force that pushes the charge around so a greater pd = a greater current
• resistance is measure in ohms
• resistance, pd and current are linked together in the equation V=IR
• when current passes through a resistor it heats up as electrons collide with the ions in the resistor as they flow through it. ions gain energy and vibrate and heat up.
• the harder ions vibrate the harder it is for electrons to get through the resistor. if the resistor is too hot no current can pass through it. this can be controlled by a thermistor