Resistance A resistor is a component in a circuit that transforms electrical energy into other types of energy. Some resistors like the heating element in a toaster transform electrical energy into thermal energy. In a light bulb, the filament transforms the electrical energy into light energy

The electric kettle A resistor is a component designed to reduce the current. A variable resistor has a resistance that can be changed. A fixed resistor has a resistance that remains the same. Many domestic appliances use resistance to transfer electrical energy to heat and light energy. The heating element in this kettle is a coil of metal that resists electricity. As current is passed through the metal, resistance causes the metal to get hot and so boils the water.

Resistance Resistance: The ability of a material to hinder the flow of electric current. Symbol: R SI unit: Ohm (Ω) –or 1 V / 1 A Circuit diagram: Resistance lowers the energy level supplied on the charges, as this energy is transformed

Name the Parts of the circuit Voltmeter Resistor Resistor Ammeter Light bulb Power Switch

Ohm’s Law Potential difference measured in Volts (V) Current intensity (I) measured in Amperes (A) Resistance measured in ohm’s (Ω)

Example What is the resistance of a circuit component if the current going through the wire is 0.50A and the electric potential around the component is 3.5V ?

Resistors (don’t write!) Resistors are often placed into a circuit to limit the flow of electrons. Some resistors have a ceramic coating with colour coded bands to indicate the resistance Determining the resistance using colour codes. The 1st and 2nd bands give you the first two digits of the resistance. The 3rd band is the exponent on ten by which the first two digits must be multiplied. The 4th band indicates the tolerance of the resistor (+/- %). This tells you how close the actual resistance will be to the value indicated by the bands.

Tolerance Colour ±1% brown ±2% red ±5% gold ±10% silver Number Colour black 1 brown 2 red 3 orange 4 yellow 5 green 6 blue 7 violet 8 grey 9 white Tolerance Colour ±1% brown ±2% red ±5% gold ±10% silver

What is the Resistance on the following resistor?

Factors that effect conductivity Not all metals conduct electricity equally. The conductivity of wires depends upon four factors: nature of the wire  copper is an excellent conductor; nichrome is a poor conductor wire diameter  thicker wires are more conductive (up to a point) wire length  shorter wires are more conductive wire temperature  colder wires are more conductive