Electric Charges and Fields Test 7

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Electric Charges and Fields Test 7

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Weekly Quiz Competition

Question 1
1 / -0

Two point charges 2μC and 8μC are placed 12 cm apart. The position of point from 2μC charge, where the electric field intensity is zero is:

A
4 cm

B
12 cm

C
2 cm

D
8 cm

Solution

Let net electric is zero at point P at a distance r from the 2mc charge.
Electric field at point P due to charge 2mc i sin direction of 8mc and its value is
Electric field at point P due to charge 8mc isin direction of 2mc and its value is

for net field to be zero
taking root on both sides
Question 2
1 / -0

Two equal positive charges q₁ = q₂ = 2.0 μC. are located at x = 0, y = 0.3 and x = 0 and y = -0.3 m respectively. What are the magnitude and direction of the total electric force (expressed in Newton and degrees counter clockwise w.r.t x - axis) that q₁ and q₂ exert on a third charge Q = 4.0 μC at x =0.4 and y = 0 m

A
0.46,0.00

B
0.44,2.00

C
0.42,1.00

D
0.48,3.00

Solution

Side AP = = 0.5m Electric Field due to charge at A on point P = Elecric Field due to charge at B on
point P
Where So force due to this field on charge P
F = qE = 4 x 10^-6 x 115.2 x 10³ F = 0.46N
Since this force in the direction of positive x axis so angle = 0^o
Question 3
1 / -0

The electric field and force experienced by a test charge placed at origin is 6 x 10⁵N/C and 18 x 10^-4 N. The value of test charge is:

A
12nC

B
6nC

C
9nC

D
3nC

Solution

By definition of Electric Field,
Question 4
1 / -0

A tennis ball which has been covered with charges is suspended by a thread so that it hangs between two metal plates. One plate is earthed, while other is attracted to a high voltage generator. The ball

A
Hangs without moving

B
Is attracted to the high voltage plate and stays there

C
Swings backward & forward hitting each plate in turn

D
Is repelled by earthed plate and stays there

Solution

The plate which connected to high voltage generator induces negative charge on ball which causes attraction. When the ball strikes the positive plate, charge distribution again takes place that is the bass becomes positive and repulsion takes place. When it strikes the plate which connected to earth than its charge goes to earth and again it will be attracted towards positive plate. Hence the ball swings backward and forward hitting each plate in turn.
Question 5
1 / -0

Which, among the following is the correct expression for electric field?

A
E=F/C

B
E=F*C

C
E=F/Q

D
E=F*Q

Solution

Electric field is the force per unit charge hence, the correct expression is: E=F/Q.
Question 6
1 / -0

A charge q is placed at the center of the line joining two equal charges Q. The system of the three charges will be in equilibrium if q is equal to

A
Q/2

B
Q/4

C
Q/5

D
Q/3

Solution

Suppose in the following figure, equilibrium of charge B is considered.
Hence for its equilibrium
Question 7
1 / -0

Electric field intensity varies with distance as:

A

B
E α r²

C

D

Solution

E = F/q = KQ/r²
Question 8
1 / -0

If electric field lines cross each other that would mean

A
The electric field can be in either of the two directions.

B
The direction of the field changes at that point

C
Two directions for the electric field at one point which is not possible.

D
The resultant electric field at a point is zero

Solution

Properties of Electric Field Lines. At every point on an electric field line, the tangent represents the direction of electric field. If two field lines cross each other at the point, then there would be two possible directions for electric field which is physically impossible.
Question 9
1 / -0

The S.I. unit of electric field intensity is:

A
NC^-1

B
NC

C
N^-1C

D
None of the above

Solution

Electric Field Intensity E = F\q
Question 10
1 / -0

The diagram shows the electric field lines in a region of space containing two small charged spheres, Y and Z then which statement is true?

A
Magnitude of electric field is same everywhere

B
Y is negative & Z is positive

C
Y and Z must have the same sign

D
A small negatively charged body placed at X would be pushed to the right

Solution

A small negatively charged body placed at X would be pushed to the right

The negative charge feels a force opposite to the direction of field.
Other cases are not possible from properties of electric lines of force.
Question 11
1 / -0

Which equation correctly shows the force on a charge q in an electric field E

A

B

C

D

Solution

E = F/q
Question 12
1 / -0

A test charge of 3nC is placed at origin and experiences a force of 9 x 10^-4 N. The electric field at origin is:

A
0.3 x 10⁵ N/C

B
9 x 10⁵ N/C

C
3 x 10⁵ N/C

D
1 x 10⁵ N/C

Solution

E =F/q = (KQ/r²)
Question 13
1 / -0

The field lines for single negative charge are:

A
Radiating outwards

B
Radiated inwards

C
Parallel

D
Spheres concentric with charge

Solution

Conventionally, field lines originate from a positive point charge and terminate at negative charge
Question 14
1 / -0

At any point on S on an electric field line

A
The perpendicular to the line is in the direction of electric field at that point

B
The tangent to the line is in the direction of electric field at that point

C
The normal to the line is in the direction of electric field at that point

D
The curvature is in the direction of electric field at that point

Solution

When a tangent is drawn at any point on field line then that tangent gives the direction of electric field at that point
Question 15
1 / -0

An electric field can deflect

A
X rays

B
α – rays (He²⁺)

C
γ - rays

D
Neutrons

Solution

Only alpha rays are moving with small velocity and having charge so they will be affected by electric field.
X Rays and Gamma Rays are electromagnetic radiations. They do not carry electric charge while neutron is a charge less particle.
Question 16
1 / -0

For uniform electric field, field lines are:

A
Divergent

B
Convergent

C
Parallel and equally spaced

D
Convergent then divergent

Solution

Uniform field lines imply that every point in space has same magnitude and direction of Electric Field. It is represented by parallel and equally spaced arrows in the direction of electric field
Question 17
1 / -0

An electron traveling north enters a region where the electric field is uniform and points North.

A
Slows down

B
Move towards East

C
Speeds up

D
Continues with the same speed in the same direction

Solution

Electron is negatively charged and force is always opposite to the direction of electric field. So the when the force acts along South and opposite to the velocity which means the electron slows down.
Question 18
1 / -0

The magnitude of an electric field balancing a deutron of charge 1.6 x 10^-19 C and mass 3.2 x 10^-27 kg is:

A
4 * 10^-8N/C

B
2 * 10^-9N/C

C
4 * 10^-9N/C

D
2 * 10^-7N/C

Solution

Given:
Charge, q = 1.6 x 10^-19 C
Mass, m = 3.2 x 10^-27kg
Question 19
1 / -0

Two charges A = -2.50 μCand B = 6.0 μC are at a distance of 1 meter from each other. Distance from A at which the electric field is zero in meters is

A
2.03

B
1.85

C
2.22

D
1.92

Solution

distance of null point from small charge, d=distance between two charges, q2=bigger charge, q1=small charge. +1 for like charges and -1 for unlike charges x
Question 20
1 / -0

Six charges are kept at the vertices of a regular hexagon as shown in the figure. If magnitude of forceapplied by +Q on +q charge is F, then net electric force on the +Q is:

A
5F

B
8F

C
9F

D
4F

Solution

Superposition of Electrostatic Force given by Coulomb’s Law for each of the charge