Which change decreases the resistance of a piece
of copper wire?
(1) increasing the wire’s length
(2) increasing the wire’s resistivity
(3) decreasing the wire’s temperature
(4) decreasing the wire’s diameter

Explanation :

We know that the resistance of the wire is given by :

Where

is the resistivity

l is the length of the wire

A is the area of the wire.

Another factor on which the resistance of wire depends is temperature. It is given by :

So, it is clear that the resistance of the wire is directly proportional to the temperature. It we want to decrease the resistance of the piece, its temperature should be decreased.

So, the correct option is (3) " decreasing the wire’s temperature ".

whitney would be experiencing fear or unintentional terror

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation: