Ohm's Law and Electrical Power

A heater takes a current of 2.77 A from a 220 V supply. What is the resistance?

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Answer explanation

To find the resistance, use Ohm's Law: R = V / I. Substituting the values, R = 220 V / 2.77 A = 79.42 ohms.

How much current does a 50 Ω electric iron take if the applied voltage is 250 volt?

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Answer explanation

To calculate the current, use Ohm's Law: I = V / R. Substituting V = 250V and R = 50Ω, I = 250V / 50Ω = 5A. Therefore, the electric iron takes 5 Amps of current.

A metal filament lamp has a resistance of 55 Ω when cold and 622 Ω when hot. If the lamp works on a 230 V supply. Find: (a) the current at the moment of switching on (b) the current when the lamp has reached its working temperature.

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Answer explanation

(a) Current at switching on = V/R = 230/55 = 4.18 A. (b) Current at working temp = V/R = 230/622 = 0.37 A.

An electromagnet of resistance 12.4 Ω requires a current of 1.5 A to operate. Find the required voltage.

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Answer explanation

The required voltage can be found using Ohm's Law: V = I * R. Therefore, V = 1.5 A * 12.4 Ω = 18.6 V.

What is an ampere equal to?

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Answer explanation

An ampere is equal to the flow of one coulomb of charge per second in a circuit.