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ELECTRICAL CIRCUIT CALCULATIONS. S.MORRIS 2006. More free powerpoints at www.worldofteaching.com. Basic Formula. Almost all calculations in circuits use Ohm’s Law V=IR Each circuit type has additional formulas dependent on what happens to voltage and current in the circuit. SERIES CIRCUITS. - PowerPoint PPT Presentation
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S.MORRIS 2006
ELECTRICAL CIRCUIT ELECTRICAL CIRCUIT CALCULATIONSCALCULATIONS
More free powerpoints at www.worldofteaching.com
Basic Formula
• Almost all calculations in circuits use Ohm’s Law
• V=IR
• Each circuit type has additional formulas dependent on what happens to voltage and current in the circuit
SERIES CIRCUITS
A series circuit has only one pathThis means that the current is the same throughout the circuitIt = I1 = I2 = I3Because current is the same, voltage at each load depends on the resistance of the load. V1 = It * R1 Vt = V1 + V2 + V3 and Rt = R1 + R2 + R3
Do the Math!!
?
?
A2
A1
4AV1
V3
V2Light bulb 1 has .5 ohms of resistance
Light bulb 2 has .9 ohms of resistance
Light bulb 3 has .6 ohms of resistance
Find V1, V2, V3, Vt, It, and Rt
It = I1 = I2 = 4ARt = .5 ohms + .9 ohms + .6 ohmsRt = 2 ohmsV1 = 4 amps * .5 ohms = 2 volts V2 = 4 amps * .9 ohms = 3.6 volt V3 = 4 amps * .6 ohms = 2.4 volts Vt = 2 V + 3.6 V + 2.4 V = 8 V
PARALLEL CIRCUITS
A parallel circuit has multiple paths Current gets split, and voltage stays the same throughout Vt = V1 = V2 = V3
Because voltage is the same, current at each load depends on the resistance of the load. I1 = Vt / R1 It = I1 + I2 + I3
PARALLEL CIRCUITS
Because a parallel circuit has multiple paths, the resistance does not add up, instead it is split (but not the same as current)The formula for total resistance is:1/Rt = 1/R1 + 1/R2 + 1/R3
Do the Math!!
V2
V1
6VIt
I2
I1
Light bulb 1 has 1 ohms of resistance
Light bulb 2 has 4 ohms of resistance
Find V1, V2, I1, I2, It, and Rt
Vt = V1 = V2 = 6 VI1 = 6 volts / 1 ohms = 6 amps I2 = 6 volts / 4 ohms = 1.5 amps It = 6 amps + 1.5 amps = 7.5 amps1/Rt = 1/1 ohms + 1/4 ohms 1/Rt = 1 ohm + .25 ohms1/Rt = 1.25 ohms1/1.25 = Rt
.8 ohms = Rt