Federal+KPK Board
Chapter 11(Electrostatics)
Question no 1:
As,
−∆v
E=
∆r
Since the electric potential throughout the region remains constant
V=constant
∆V = 0
−0
E = ∆r
E=0
So, Electric field is zero when potential is constant.
Question no 2:
Yes, it will perform a rectilinear Motion because, Electric field lines never cross each other & always
points a single direction so when a point charge is released it generates radial electric field lines So, charge
will perform rectilinear motion.
Question no 3:
Potential difference is basically change in energy and is a relative quantity while electric potential
energy doesn't explain change more precisely. Potential difference is basically energy per unit charge while
electric potential energy is energy stored in charge.
∆U
∆V =
Q
Question no 4:
Volt: The potential difference will be 1V if work done by a charge of 1C is 1J.
W
V=
q
Electron Volt: The Energy gain or loss by an electron When it moves through a potential of 1V.
Electron volt =Charge x volt
Question no 5:
When a negative charge is moved in Electric field then near the positive plate its Electric Potential is
high but Electric Potential Energy is very low whereas when positive charge is moved near the positive plate
both Electric Potential & Electric potential Energy is high.
Question no 6:
The potential of non-uniformly sphere behave as point charge from outside the surface because
charge sphere will behave as a point charge.
1 q
v=
4πε∘ r
But the potential of non-uniformly sphere is not same point charge from inside the surface of sphere because
it does not behaves as a point charge.
Question no 7:
As,
1 2
U= CV
2
Parallel Combination:
In parallel combination equivalent capacitance of capacitor is greater, so energy stored is maximum.
Series Combination:
In series combination equivalent capacitance of capacitor is smaller, so energy stored is minimum.
So, Energy stored in parallel combination is greater that series combination.
, Question no 8:
No, Equipotential lines can never cross each other. Because at point of intersection electric charge has more
than one direction which is physically not possible. It also means that at point of intersection electric
potential has two values.
Question no 9:
As,
Workdone ∝ Er
If the water has larger value of Er then, charges have to do work, this work ionizes the water due to which it
starts conduction but dielectric must be insulator that’s why we can’t use it as dielectric.
Question no 10:
Capacitors of capacitor will be increases by:
1. Increasing the area of plates.
2. Decreasing the separation b/w charges.
3. Use dielectric having larger value of dielectric constant.
Aε∘ εr
C=
d
Chapter 12(Current Electricity)
Question no 1:
Given Data:
I = 3A
t = 24h=24×60×60=86400s
e = 1.6 × 10−19
Solution:
Q ne
As, I=
t
=
t
It
So, n= e
(3)(86400)
n = 1.6×10−19
n = 1.62 × 1024
Question no 2:
Internal Resistance:
The resistance offered by a battery in a circuit is called internal resistance.
“The internal resistance is very low as compare to resistance of circuit that’s why internal resistance is
ignored by battery while analyzing he emf.
Question no 3:
��
As, ρ= �
���2
ρ = 4�
ρ ∝ d2
As, the resistivity is directly proportional to the diameter of wire that’s why aluminium has large diameter as
compare to copper wire. Because resistivity of aluminium is 0.02854Ωm & copper is 0.0451Ωm.
Question no 4:
Wherever, battery in a circuit is charged, terminal potential difference of a battery exceed it’s emf.
As, �� = � − ��
Charging, �� = � − ( − �)� “�= −�"
�� = � + ��
So, �� > �
Chapter 11(Electrostatics)
Question no 1:
As,
−∆v
E=
∆r
Since the electric potential throughout the region remains constant
V=constant
∆V = 0
−0
E = ∆r
E=0
So, Electric field is zero when potential is constant.
Question no 2:
Yes, it will perform a rectilinear Motion because, Electric field lines never cross each other & always
points a single direction so when a point charge is released it generates radial electric field lines So, charge
will perform rectilinear motion.
Question no 3:
Potential difference is basically change in energy and is a relative quantity while electric potential
energy doesn't explain change more precisely. Potential difference is basically energy per unit charge while
electric potential energy is energy stored in charge.
∆U
∆V =
Q
Question no 4:
Volt: The potential difference will be 1V if work done by a charge of 1C is 1J.
W
V=
q
Electron Volt: The Energy gain or loss by an electron When it moves through a potential of 1V.
Electron volt =Charge x volt
Question no 5:
When a negative charge is moved in Electric field then near the positive plate its Electric Potential is
high but Electric Potential Energy is very low whereas when positive charge is moved near the positive plate
both Electric Potential & Electric potential Energy is high.
Question no 6:
The potential of non-uniformly sphere behave as point charge from outside the surface because
charge sphere will behave as a point charge.
1 q
v=
4πε∘ r
But the potential of non-uniformly sphere is not same point charge from inside the surface of sphere because
it does not behaves as a point charge.
Question no 7:
As,
1 2
U= CV
2
Parallel Combination:
In parallel combination equivalent capacitance of capacitor is greater, so energy stored is maximum.
Series Combination:
In series combination equivalent capacitance of capacitor is smaller, so energy stored is minimum.
So, Energy stored in parallel combination is greater that series combination.
, Question no 8:
No, Equipotential lines can never cross each other. Because at point of intersection electric charge has more
than one direction which is physically not possible. It also means that at point of intersection electric
potential has two values.
Question no 9:
As,
Workdone ∝ Er
If the water has larger value of Er then, charges have to do work, this work ionizes the water due to which it
starts conduction but dielectric must be insulator that’s why we can’t use it as dielectric.
Question no 10:
Capacitors of capacitor will be increases by:
1. Increasing the area of plates.
2. Decreasing the separation b/w charges.
3. Use dielectric having larger value of dielectric constant.
Aε∘ εr
C=
d
Chapter 12(Current Electricity)
Question no 1:
Given Data:
I = 3A
t = 24h=24×60×60=86400s
e = 1.6 × 10−19
Solution:
Q ne
As, I=
t
=
t
It
So, n= e
(3)(86400)
n = 1.6×10−19
n = 1.62 × 1024
Question no 2:
Internal Resistance:
The resistance offered by a battery in a circuit is called internal resistance.
“The internal resistance is very low as compare to resistance of circuit that’s why internal resistance is
ignored by battery while analyzing he emf.
Question no 3:
��
As, ρ= �
���2
ρ = 4�
ρ ∝ d2
As, the resistivity is directly proportional to the diameter of wire that’s why aluminium has large diameter as
compare to copper wire. Because resistivity of aluminium is 0.02854Ωm & copper is 0.0451Ωm.
Question no 4:
Wherever, battery in a circuit is charged, terminal potential difference of a battery exceed it’s emf.
As, �� = � − ��
Charging, �� = � − ( − �)� “�= −�"
�� = � + ��
So, �� > �
