Question

A 240v, 60w lamp has a working resistance of:

Answer 1

Answer:

The lamp has a working resistance of 960 ohms.

Explanation:

Let us solve the given problem in 2 methods to get a solution

Method 1:

We have p= $\frac{v^{2}}{R}$

Therefore R= $\frac{v^{2}}{p}$

Where R is the resistance of the bulb, p is the power consumption in watt W, V is the voltage which is expressed in terms of volts V

From the given problem we have p=60 W v=240 V

By substituting the values in the equation we get

R= $(240)^{2} / 60$

=960 ohms

Method 2:

We have P=IV

Substitute the values

60=240I

I=60/240

=0.25

But we know that

V=RI

240=R x 0.25

R=240/0.25

=960  

Hence the resistance of the bulb=960 ohms  

Answer 2

Answer:

The lamp has a working resistance of 960 ohms.

Explanation:

Let us solve the given problem in 2 methods to get a solution

Method 1:

We have p= \frac{v^{2}}{R}

R

v

2

Therefore R= \frac{v^{2}}{p}

p

v

2

Where R is the resistance of the bulb, p is the power consumption in watt W, V is the voltage which is expressed in terms of volts V

From the given problem we have p=60 W v=240 V

By substituting the values in the equation we get

R= (240)^{2} / 60(240)

2

/60

=960 ohms

Method 2:

We have P=IV

Substitute the values

60=240I

I=60/240

=0.25

But we know that

V=RI

240=R x 0.25

R=240/0.25

=960

Hence the resistance of the bulb=960 ohms