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For an incandescent 40W lamp at 120V the resistance would be 360 ohms when hot, and the current would be 333 mA.

## How much resistance is a 40 watt light bulb?

The 40 W bulb: 120^2/40 = 360 Ohms.

## What is the resistance of bulb 40W 220v?

Answer: Resistance of the bulb (R) = 1222 Ohms.

## How is resistance of a bulb calculated?

Since it involves the relationship of power voltage, current, and resistance, using the formula I=P/V with P and V known to find the current, and then using the formula R=P/I^2 to find the resistance will be the right steps to take.

## What is the resistance of 100 watt bulb?

100 watts = I * 110 volts. 100 / 110 = 0.909 amps. 110 / 0.909 = ~ 121 ohms for the 100 watt bulb.

## What is the resistance of a 40 watt light bulb at 120 volts?

Since power, P, equals iV, P/V = i, so at 120 V, a 40-watt bulb draws 1/3 A. (The units in iV are (C/s)(N-m/C), or J/s, which are watts.) For a given resistance, V = iR, so the bulb’s resistance (when it has 120 volts across it) is 120/(1/3), or 360 ohms.

## What is the resistance of a 40W 120V bulb when it is lighted?

A rough estimate is that hot resistance is about 10x larger than the cold resistance. It also means the switches and wires see roughly 10x larger current surge when the light is turned on. So a 40W bulb at 120V would be 360 ohms, and you measure 26 ohms when cold.