The higher the energy, the greater the voltage (potential difference). the measure of energy measure of “potential difference The unit for voltage is volts (V) Potential difference flows from high energy to low energy The potential difference (voltage) is 1.5 V for a battery. The higher the energy, the greater the voltage (potential difference).

is the rate of the flow of an electrical charge. Current is the rate of the flow of an electrical charge. + How fast (speed) is the electricity flowing through these wires? How fast is this water coming out? CURRENT (I) is measured in Amperes or Amps (A).

 Resistance Resistance (R) is measured in ohms. The slowing down or stopping of current. Resistance (R) is measured in ohms. 

Match the word on the left to the phrase on the right. Resistance How Fast? (R) in Ohms  Current How much? (I) in Amps Voltage How much is it slowed down? (V) in Volts

Electrical Measuring Instruments Voltmeter-used in parallel to measure voltage Ammeter-used in series to measure current Galvanometer-used to detect a current Ohmmeter-measures resistance

We can use this formula to figure out voltage, current and resistance. Georg Simon Ohm Ohm's Law I R V / = We can use this formula to figure out voltage, current and resistance.

Ohm’s Law Information If voltage goes up, the charges move a little faster between atoms and we get more current. A current vs. voltage graph shows us if resistance changes. Resistance of metals increases with temperature, because the particles collide more often causing more resistance.

Calculating Ohms Law I = V / R So, to find Current, we need to divide voltage by resistance. I = V / R Divide Multiply V volts And, to find Resistance, we need to DIVIDE voltage by current. R = V I I amps R ohms To find voltage we multiple current and resistance. V = IR

Calculate the potential difference (voltage) across a 3  resistor if a 0.5 A current is flowing through it. I = V / R What do you know? V = 0.5 A x 3  V = ? I = 0.5 A R = 3  V = 1.5 Volts

A radio with a resistance of 240  is plugged into a 120 V outlet A radio with a resistance of 240  is plugged into a 120 V outlet. What is the current flowing from the outlet? I = V / R What do you know? I = 120 / 240 V = 120 V I = ? R = 240  0.5 amps = I

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Electrical Power is rate at which energy flows Power (P) is measured in Watts (W) Power = current x voltage P = I x V Divide Multiply So, to find Current, we need to DIVIDE power by voltage. I = P V P watts I V And, to find Voltage, we need to DIVIDE power by current. V = P I amps volts

Where do Power Units come from? Power = Voltage x Current Joules Joules Coulomb second Coulomb second (Watts) (volts) (amps) = x

Electrical Power Problem If a CD player uses 4.5 V with 0.2 amps of current, what is the power it uses? P= I x V P = ? P = 0.2 A x 4.5 V I = 0.2 A P = 0.9 Watts V = 4.5 V

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Is measured in kilowatt-hours Electrical Energy = power x time Kilo means 1000x Electrical Energy = power x time E = P x t Divide Multiply So, to find power, we need to DIVIDE energy by time. P = E t E kWhr And, to find time, we need to DIVIDE energy by power. t = E P P kW t hr

Electrical Energy Problem You use your hairdryer for 10 minutes everyday. The hairdryer uses 1000 watts. How many kilowatt-hours does your hairdryer use in 12 days? E = P x t E = 1 kW x 0.17 hr E = P = 1000 W = 1 kW 0.17 x 12 days= 2 kWhr t = 10min / 60 = 0.17 hr

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