A 60-cm-long heating wire is connected to a 120 V

Alfred Martin

Alfred Martin

Answered question


A 60-cm-long heating wire is connected to a 120 V outlet. If the wire dissipates 45 W, what are (a) the current in and (b) the resistance of the wire?

Answer & Explanation

Cheryl King

Cheryl King

Beginner2022-01-11Added 36 answers

Step 1
In this problem we have to calculate the electric current I and resistance of a wire R. The following data are:
Length of wire: l=60cm=0.6m
Outlet voltage: V=120V
Dissipation of power: P=45W
Step 2
To calculate a) we can use the following equation:
I=PV (1)
Step 3
To calculate b) we can use Ohms


Beginner2022-01-12Added 30 answers

Concepts and reason
The concepts required to solve the given problem are ohms law and power.
Initially, calculate the current in the wire by using the relation between power, voltage, and current. Finally, calculate the resistance of the wire by using ohms law.
According to ohm’s law, the current passing through the conductor is directly proportional to the voltage.
Here, V is the voltage, I is the current, and R is the resistance.
The rate of electrical energy dissipated is called as power.
The expression for the power is,
Here, E is the electrical energy and t is the time.
The expression for the electrical energy is,
E = V I t
The expression for the power is,
Rearrange the above equation for the current.
​Substitute 45 W for P and 120 V for V.
From the ohms law, the voltage is,
Rearrange the above equation for the resistance.
Substitute 120V for V and 0.375A for I.
Answer: Part A
The current in the wire is 0.375A.
Part B
The resistance of the wire is 320Ω.

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