Answer:

Explanation:
At the bottom the tension would be upwards and the weight downwards, their difference being the centripetal force. Taking the upwards direction as positive we then have:

where we have used the equation for centripetal acceleration. Thus we have:

Explanation:
The resistance of a wire is given by :

Where
is the resistivity of the wire
l = initial length of the wire
A = initial area of cross section
If length and the area of cross section of the wire is doubled then new length is l' and A', l' = 2 l and A' = 2 A
So, new resistance of the wire is given by :


R' = R
So, the resistance of the wire remains the same on doubling the length and the area of wire.
Answer : The cell emf for this cell is 0.077 V
Solution :
The balanced cell reaction will be,
Oxidation half reaction (anode): 
Reduction half reaction (cathode): 
In this case, the cathode and anode both are same. So,
is equal to zero.
Now we have to calculate the cell emf.
Using Nernest equation :
![E_{cell}=E^o_{cell}-\frac{0.0592}{n}\log \frac{[Zn^{2+}{diluted}}{[Zn^{2+}{concentrated}]}](https://tex.z-dn.net/?f=E_%7Bcell%7D%3DE%5Eo_%7Bcell%7D-%5Cfrac%7B0.0592%7D%7Bn%7D%5Clog%20%5Cfrac%7B%5BZn%5E%7B2%2B%7D%7Bdiluted%7D%7D%7B%5BZn%5E%7B2%2B%7D%7Bconcentrated%7D%5D%7D)
where,
n = number of electrons in oxidation-reduction reaction = 2
= ?
= 0.0111 M
= 4.50 M
Now put all the given values in the above equation, we get:


Therefore, the cell emf for this cell is 0.077 V