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Regents Physics. Parallel Circuits Ohm’s Law in Parallel Circuits. Parallel Circuits. Summary 1. The potential drops of each branch equals the potential rise of the source. 2. The total current is equal to the sum of the currents in the branches
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Regents Physics • Parallel Circuits • Ohm’s Law in Parallel Circuits
Parallel Circuits Summary 1. The potential drops of each branch equals the potential rise of the source. 2. The total current is equal to the sum of the currents in the branches 3. The inverse of the total resistance of the circuit (also called effective resistance) is equal to the sum of the inverses of the individual resistances.
Voltage in a Parallel Circuit • What is the voltage drop across the resistor and light bulb? • Draw a voltmeter that would measure the potential difference across the resistor only Answer: 12 VOLTS V 12 V cell
Current in a Parallel Circuit • Current in divided in the branches • Resistance of individual resistors determines how much current will flow through it • Question: What has higher resistance • the resistor or the light bulb? • Draw an ammeter measuring • the current through the light bulb • the total current in the circuit 12 V cell e- e- e- e- e- e-
Equivalent Resistance • A short-cut method to using the equation • Find the average of the resistors • Divide by number of resistors is the same as… is the same as…
Equivalent Resistance con’t • More than 2 resistors is the same as… 5+7+12= 24 24/3 = average = 8 8/3 resistors = between 2 - 3 is approximately…
Example of a Parallel Circuit R1 = 2 1) Find current flowing through each resistor 2) Find the total current flowing in the circuit 3) Find the equivalent resistance of the circuit R2 = 3 R3 = 6 12V