Given
Three 7 ohm resistor are in series.
The battery is V=10V
To find
The equivalent resistance
Explanation
When the resistance are in series then the resistance are added to find its equivalent.
Thus the equivalent resistance is:

Conclusion
The equivalent resistance is 21 ohm
Well first graph represents rectangular hyperbola
vu = c^2 ( c is constant)
AS 1/v + 1/u = 1/f
Take1/ f to be constant c
1/v = c - 1/u
it is of the form y = - x + k
Slope = -1 having intercept k as shown in fig 2
The length of the wire is 36 m.
<u>Explanation:</u>
Given, Diameter of sphere = 6 cm
We know that, radius can be found by taking the half in the diameter value. So,

Similarly,

We know the below formulas,


When equating both the equations, we can find length of wire as below, where 


The
value gets cancelled as common on both sides, we get

The
value gets cancelled as common on both sides, we get

Answer:
The electric field at origin is 3600 N/C
Solution:
As per the question:
Charge density of rod 1, 
Charge density of rod 2, 
Now,
To calculate the electric field at origin:
We know that the electric field due to a long rod is given by:

Also,
(1)
where
K = electrostatic constant = 
R = Distance
= linear charge density
Now,
In case, the charge is positive, the electric field is away from the rod and towards it if the charge is negative.
At x = - 1 cm = - 0.01 m:
Using eqn (1):

(towards)
Now, at x = 1 cm = 0.01 m :
Using eqn (1):

(towards)
Now, the total field at the origin is the sum of both the fields:
