Chapter 7 Electricity

What is Charge? Protons have a (+) charge Electrons have a (-) charge Charge (q) is measured in Coulombs The elementary charge of one (+) or (-) is 1.6 x C 1 Coulomb = 6.25 x10 18 electrons Opposite Charges Attract Like Charges Repel

Static Electricity the accumulation of excess electrons on an object

Current The flow of charges, usually electrons, through a wire or conductor is called electric current Electric current is measured in amperes (A). Potential Difference is the push that causes charges to move. Voltage is measured in Volts (V)

Resistance The greater the restriction of charges to flow the lower the amount current that can flow. Resistance is measured in ohms (Ω) The length, diameter, and temperature of a wire influences it’s resistance. Types of resistors: Light bulbs Door bells Any electrical device

Types of Currents Direct Current (dc) is the type of electricity that we get from batteries. In a direct current all of the electric charges move in one direction.

Types of Current Alternating Current (ac) is the type of electricity that we get from plugs in the wall. In an alternating current all of the electric charges switch their direction of flow back and forth.

Ohm’s Law V = I  R I = V / R R = V / I Ohm’s Law – the current in a circuit equals the voltage difference divided by the resistance.

Ohm’s Law I = Current (Amperes) V = Potential Difference (volts) R = Resistance (ohms Ω)

Circuits

Total Resistance in Circuits Series R S = R 1 + R 2 + R 3 + … Total resistance increases as more resistors are added to the series circuit Parallel 1/R P = 1/R 1 + 1/R 2 +1/R 3 +… Total resistance decreases as more resistors are added to the parallel circuit