CURRENT, VOLTAGE & RESISTANCE

Learning Goals ■I will be able to explain the difference between voltage, current and resistance. ■I will be able to explain the factors affecting resistance.

Voltage (Potential Difference) ■Voltage (Potential Difference): The difference in energy per electron at two points. ■Measured in volts using a voltmeter.

Electric Current ■Electric Current: A measure of how fast electrons are moving past a given point. ■Measured in Amperes (A). –1A = electrons are flowing every second. ■Measured using a device called an Ammeter.

Ammeter Symbol (connected in series) Voltmeter Symbol (connected in parallel)

Electric Current at Home ■Houses have safeguards installed in case too much current is being used. –Fuses (older homes) vs Circuit breakers (newer homes) –Circuit breakers are switches which turn off if too much current exists. ■Most homes have a total of A of electricity entering from their providers.

The Human Body ■The human body has it’s own electrical signals that exist naturally. ■Even small electrical shocks to the system are dangerous: –0.001A: Small tingling sensation – A: Can cause muscles to contract –1-4.3A: Can stop your heart if passed through chest. ■An outlet that powers a computer can deliver 15A of current.

Resistance in Circuits ■Resistance: The ability of a material to oppose the flow of electric current. ■Measured in Ohms (Ω).

Factors that Affect Resistance ■There are 4 key factors that affect resistance: 1.Type of Material: Insulator vs. conductor. 2.Cross-sectional area: The larger the diameter, the less resistance. 3.Length: The shorter the length, the less resistance. 4.Temperature: The colder the wire, the less resistance.

Learning Goals Revisited ■I will be able to explain the difference between voltage, current and resistance. ■I will be able to explain the factors affecting resistance.

Please Complete ■P557 #1,3,4 ■P561 #2,4 ■P566 #2,3,4,6,7