Section 13.2

 List the units used to measure current and voltage.  Describe how to measure current and voltage in a circuit.  Explain the function of a battery in a circuit.

 This is what carries energy in a circuit.  Units: Amperes (A), “amp” Ex. A small flashlight uses around ½ amp of electric current.

 In batteries, current flows out of the positive end and back through the negative end.  The amount of current flowing out must always equal the amount flowing back in. Imagine golf balls being pushed through a hose. As one is pushed in, one will pop out.

 Measures the difference in electrical potential energy between two places in a circuit. This difference is what allows energy, current, to flow.  Units: Volts (V)

 With electricity, energy becomes useful when we let the voltage difference cause current to flow in a circuit.  Current is what flows and actually does work.

 1 volt, means 1 amp of current does 1 joule of work in 1 second.  1 joule/sec = 1 watt (power)  Thus, Voltage is the power per amp of current that flows. Ex: Every amp of current that flows out of a 1.5v battery carries 1.5watts of power. ↑ voltage = ↑ power carried by each amp.

 Voltmeter – measures voltage.  Multimeter – measures voltage or current.  When both probes are touched to each end of a battery, the meter reads the difference in voltage between the two places.

 A battery uses chemical energy to create a voltage difference between its terminals. Current flows out, carrying energy. That energy is used in the circuit. Current returns to the battery and picks up more energy.

 To measure current you need to break the circuit and allow the energy to flow through the meter.  Some meters, called ammeters, are designed to specifically measure current.

 Page 305, questions 1-4.  In addition to the diagram you have to draw for question 4, also draw a diagram show how you would measure voltage in the circuit. This may be done with one diagram if you choose. You MUST use symbols and NOT pictures.