Electrical Resistance
- Created by: Clare
- Created on: 28-03-13 14:05
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- Electrical Resistance
- Voltage
- Current varies in PROPORTION to voltage
- In a metal wire when it doesn't get hot
- When voltage is connected across a wire, current flows through the wire
- Different wires allow for different sized currents to flow for a given voltage
- Current varies in PROPORTION to voltage
- Resistance
- Measured in Ohms
- Voltage= current x resistance
- Uses of resistors
- Variable resistors allow you to change the amount of resistance using a rotary or sliding action
- Lamp dimmer circuits
- Volume control in audio equipment
- Speed control in car games
- Thermistors
- Resistance decreases as temperature increases
- Turn something ON in heat
- Made from semi-conductors
- Uses
- Fire alarms
- Turning on a fan/ cooling system
- Resistance decreases as temperature increases
- Light Dependent Resistors
- Made from a semi-conductor
- More light= less resistance
- Uses
- Light sensing cicuits
- Turning on street lights at night
- Automatic security lights
- Diodes and LEDs
- Only allow an electric current in the direction of the arrow
- They have huge resistance in one direction and very low in the other
- They are used as indicators to show when a device is turned on
- Diodes are used in power supplies for DC equipment
- Graphs
- Resistance in a wire (Resistance- length)
- Resistor (Current- voltage)
- Bulb (Current- voltage)
- Diode (current- voltage)
- LDR (resistance- light)
- Thermistor (Resistance- temperature)
- Voltage
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