What is the max voltage for 3 50ohmn resisters?

Answer 1

It depends on the power rating of the resistors. The total power of a series or parallel combination of resistors is the sum of the power rating of each. Here is one possible answer that assumes the resistors are rated at 1/4 watt and are connected in series.

Power = Current ^ 2 x Resistance. The ^ means squared.

Current = square root (Power / Resistance)

Current = square root (0.25 / 50) = 0.0707 amps

The total power of the three resistors in series is 0.25 x 3 = 0.75 watts

Current = square root (0.75 / 150) = 0.0707 amps <-- Notice you get the same current as before. This must be true because the current flowing through a series circuit is the same in each component.

Since Voltage = Current x Resistance

Voltage = 0.0707 x 50 = 3.54 volts across one of the resistors

OR

Voltage = 0.0707 x 150 = 10.61 volts across the series combination.

Here's another way to calculate the answer.

Voltage = square root of (Power x Resistance)

Voltage = square root (0.25 x 50)

Voltage = 3.54 volts

This is the maximum voltage across one of the resistors. If the three resistors are connected in series, the total resistance would be 150 ohms and the maximum voltage across the series combination would be 3.54 x 3 = 10.61 volts.

If the resistors are connected in parallel, the equivalent resistance is 16.67 ohms. Since the voltage across parallel resistors is the same, the maximum voltage for three 1/4 watt resistors would be square root (0.75 x 16.67) = 3.54 volts. This is the same answer calculated for the resistors in series.

The maximum current through each resistor is V / R = 3.54 / 50 = 0.0707 amps or the same current as the series combination. However, in this case, the total current flowing through the parallel combination is 0.0707 x 3 = 0.2121 amps and Power = I ^ 2 x R = .2121 ^ 2 x 16.67 = 0.75W. This proves that the powers add no matter if the resistors are in series or parallel.

If the resistors are rated at 1/2 watt the maximum voltage across one resistor is 5 V and the maximum across the series combination is 15 V. The maximum current is 0.1 A.