Ohm's Law
-R ( Resistance ) = V ( Voltage ) / I ( Current)
-V ( Voltage ) = IR
Where R is a constant: the resistance of the conductor. The units of resistance is the "ohm" W:
1 W =1 V/A
Energy and Power in electric circuits
Example 1: A resistor
V = IR
Power: P = VI = I2 R
A light bulb of resistance R = 576 W is connected to 240 V socket. Find the current through the bulb and the power expended.
Current: I = V/R = 240/576 = 0.416 A
Power: P = VI = 240 x 0.416 = 100 Watts (J/s)
Power is supplied by the battery. Magnitude of power output is
P = VI = eI
Where e is the e. m. f. of the battery.
Example 1: A resistor
V = IR
Power: P = VI = I2 R
A light bulb of resistance R = 576 W is connected to 240 V socket. Find the current through the bulb and the power expended.
Current: I = V/R = 240/576 = 0.416 A
Power: P = VI = 240 x 0.416 = 100 Watts (J/s)
Power is supplied by the battery. Magnitude of power output is
P = VI = eI
Where e is the e. m. f. of the battery.
Resistors in series and parallel
A combination of resistors in a circuit acts as the equivalent of a single resistor.
For two resistors in series the current I is the same for both:
V1 = IR1
V2 = IR2
Total voltage V drop
V = V1 + V2 = I (R1 + R2) = IR
R = R1 + R2
Resistors in series add.
If two resistors are in parallel, the voltage drop V is the same for both:
V = I1R1
V = I2R2
The total current
Resistors in parallel add as reciprocals.
The more the resistance there are, the more the alternative paths there are for the current to flow.Therefore,the more the resistance there are, the lower the total resistance and hence the higher the flow of the current.
I lazy to write the defintion lah, so i write the formulas only lor...
HaHas xD
