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Cells have positive and negative electrodes. Electrons build up on the negative electrode. Current is the amount of e - moving – coulomb Current is measured.

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Presentation on theme: "Cells have positive and negative electrodes. Electrons build up on the negative electrode. Current is the amount of e - moving – coulomb Current is measured."— Presentation transcript:

1 Cells have positive and negative electrodes. Electrons build up on the negative electrode. Current is the amount of e - moving – coulomb Current is measured in Amperes. Voltage is the difference between the potential energy of electrons at two point in a circuit.

2 + electrode - electrode electrolyte paste 5.5 Volt battery 5.5 Volts 0 Volts

3 ●● + - ●● + - e-e- e-e- Closed circuit (on) Open circuit (off) Circuits can either be opened or closed by a switch.

4 Resistors, loads and Ohm’s Law

5 Electrons lose energy as they move through things. Resistor: electrical device in a circuit that takes potential energy from electrons – resistance. Electrical symbol – R Unit is the ohm (Ω) The loss of potential energy over a resistor is called the “voltage drop” Schematic Symbol

6 Resistors are sometimes used to reduce the energy of a circuit for safety reasons. Any resistor that takes the energy and converts for use – load. Mechanical EnergyThermal Energy

7 ●● + - e-e- e-e- Load a resistor that converts energy. Resistor lowers energy removed as heat

8 Ohm’s Law - The voltage in a wire is equal to current multiplied by resistance. I R V V = I · R I = V R R = V I

9 A bulb that has 2.4 A flowing through it, has a resistance of 16 Ω. Calculate the voltage drop across the load – energy lost by the electrons to light up the bulb. ●● + - e-e- e-e- V = I · R = (2.4 A) · (16 Ω) = 38.4 V 38.4 V

10 A 9 V battery is hooked up to a metal wire to make a circuit. If the metal wire has a resistance of 6.5 Ω, calculate the current in the wire. ●● + - e-e- e-e- I = V R 9 V 6.5 Ω = = 1.38 A

11 I R V Voltage – Energy lost by the electrons through the circuit. Current – Number of electrons moving through the circuit. Resistance – the ability of a load or resistor to take energy.


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