Answer:

Explanation:
The resistance of a metal rod is given by

where
is the resistivity
L is the length of the rod
A is the cross-sectional area
The resistivity changes with the temperature as:

where in this case:
is the resistivity of silver at 
is the temperature coefficient for silver
is the current temperature
Substituting,

The length of the rod changes as

where:
is the initial length at 
is the coefficient of linear expansion
Substituting,

The cross-sectional area of the rod changes as

So, substituting,

Therefore, if the initial resistance at 21.0°C is

Then the resistance at 180.0°C is:

Answer:
Refer to the attachment!~
Answer:
a. 05cm from x axis
b. 8cm from x axis
Explanation:
If the net magnetic field is zero and the currents are in the same direction then the thanks point is between the currents i1 and i2 as show in the attachment below
a. Given that i1= 5A and i2=3A
Let assume the null point is xcm from current i1, then the null point will be (4-x)cm from current i2 since the total length is 4cm.
Now the magnetic field of the current i1 from the null point= to magnetic field of current i2 from the null point
B1=B2
μi1/2πx=μi2/2π(4-x)
i1/x=i2/(4-x)
5/x=3/(4-x)
20-5x=3x
8x=20
8x=2.5cm
since from the left of x axis is 2cm, then the null point is 2.5-2 which 0.5cm from the origin x axis.
The null point is 0.5cm from the origin x axis
b. If both current are flowing in opposite direction, the null point lies outside of the current.
Then with same analysis let assume the first current i1 is xcm from the null point and since the total length is 4cm the second current i2 will be (x-4)cm from the null point.
Also the magnetic field of the current i1 from the null point = to magnetic field of current i2 from the null point
B1=B2
μi1/2πx=μi2/2π(x-4)
i1/x=i2/(x-4)
5/x=3/(x-4)
5x-20=3x
2x=20
x=10cm.
This shows that the distance of the null point from current i1 is 10cm and the current i1 is 2cm from the x axis, then the null point is 10-2=8cm from the origin x axis.
The null point is 8cm from the x axis.
Check the attachment to see the diagram of the current and the null points
1. B. T
The period of a simple pendulum is given by:
(1)
where
L is the length of the pendulum
g is the gravitational acceleration
From the formula, we notice that the period of the pendulum does not depend on the mass of the bob. Therefore, when the bob's mass is doubled, the period does not change.
2. C: sqrt(6)*T
In this case, the pendulum is brought to the moon, where the gravitational acceleration is

If we substitute this value into the equation for the period (1), we find the new period of the pendulum:

3. B: It will no longer oscillate because there is no gravity in space
Explanation:
The motion (oscillation) of the pendulum is caused by the force of gravity, which "pulls" the bob towards the equilibrium position. If there is no gravity, then there is no force acting on the bob, therefore the pendulum can no longer oscillate.
So, the correct answer is
B: It will no longer oscillate because there is no gravity in space