The electric power consumed by a device may be calculated by using either of the two expressions P = 12R or P =V2/R . The first expression indicates that it is directly proportional to R whereas the second expression indicates inverse proportionality. How can the seemingly different dependence of P on R in these expressions be explained?
Step 1: First Case: When current I remains constant, the expression P=I2R is used. Since the current is the same for all components in a series circuit. so this expression for electric power is used in series circuit connections. Step 2: Second case: When voltage remains constant, the expression P=V2Ris used. The total current in a parallel circuit is the sum of the individual current in each component. Hence, this expression for electric power is used in the parallel circuit.
