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Cells have positive and negative electrodes .

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.

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Cells have positive and negative electrodes .

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

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

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

  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 Energy Thermal Energy

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

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

  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- + ● ● I · R V = - 38.4 V = (2.4 A) · (16 Ω) = 38.4 V e-

  10. A 9 Vbattery 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- + V R I = ● ● - 9 V 6.5 Ω = e- = 1.38 A

  11. 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. V I R

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