Astudent is experimenting with some insulated copper wire and a power supply. she winds a single layer of the wire on a tube with a diameter of dsolenoid = 10.0 cm. the resulting solenoid is ℓ = 90.0 cm long, and the wire has a diameter of dwire = 0.100 cm. assume the insulation is very thin, and adjacent turns of the wire are in contact. what power (in w) must be delivered to the solenoid if it is to produce a field of 7.40 mt at its center? (the

Explanation:

Given that:

Diameter of the solenoid,

length of the solenoid,

diameter of the wire,

magnetic field at the center of the solenoid,

Now we need the no. of turns incorporated in the length of 90 cm:

For solenoids we have:

...............................(1)

where:

permeability of the medium

n = no. of turns per unit length

I = current in the coil

So,

Now putting the respective values in the eq. (1)

We know that resistance is given by:

.....................................(2)

where:

l = length of the conducting wire

a = cross sectional area of the conducting wire

Now we need the length (l) of the wire:

Circumference of the solenoid,

&

Cross-sectional area of wire:

Resistance from eq. (2):

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27