Electrical Engineering - Series Circuits - Discussion

1. Since voltage is constant (120 v) and P = V^2/R which implies that power is inversely proportional to resistance. henceforth power will dissipate more when resistance is least i.e option A.

OR
2. P = I^2R. here power depends on the square of the current and current is inversely proportional to the current(ohm's law). I = more when resistance is less hence more current = more power PERIOD.

P = V^2/R.

Choose the lowest total resistance to maximize the dissipation.

Keeping voltage constant power is inversely proportional to resistance, so resistance increases power decrease.

@ALL.

Power, P has two formulas:
#1>> P=V^2/R and
#2>>P=I^2*R

The first relation is valid when Voltage is constant for all resistors (i.e., for Parallel combination of Rs and V.

2nd Relation is for the series circuit when Current, I is constant for all resistors.

In this question, 2nd relation is being used,
Now, by increasing Resistance, P increases, Its true But.
Value of current decreases " Square times".Hence, the Overall value of Power dissipation decrease with increase in resistance for series circuits.

I hope this will help.

In series, current will remain the same hence;
P=i^2r.

Hence resistance directly proportional to power dissipation.

Then, How option A is correct?

For a single resistor voltage drop is maximum across that resistor, so power is maximum. But when two or more resistor come into picture then voltage drop across the resistance will be lesser than previous one so power will be less.

Can any one explain? What happens if parallel combination is there?

P = V^2/R.

If R decreases then Power increases.

P = I^2.R.

If R decreases then current increases since I^2 is considered for power calculation, increase in current will be considered over increase in resistance.

Very simple thing friends P = V*I.

In this case we can increase power by two process either by increasing current or by increasing voltage though power is directly proportional to the current & voltage.

But in this question voltage is constant so we have to consider the current for solve this question. And current is higher in one resistance in comparision to series combination of 4 resistance. So the answer is "A".

v = IR = I = V/R as are reduces I increases.

And P = I^2 *R.

As R reduces I increases as p increases.