Magnetic Effects of Electric Current Test

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Magnetic Effects of Electric Current Test - 34

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Question 1
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Household appliances are usually not connected in series because:

A
Power consumption would be very much greater

B
A fuse would blow as soon as one appliance is used

C
Switching off an appliance would switch off the rest

D
The appliances would get damaged due to high current

Solution

Household appliances are not connected in series because:
1. Switching off one appliance would break the entire circuit and cause all others to turn off.
2. Resistance of appliances adds up to give an effective resistance that cannot be handled.
$$R_{eff}=R_{1}+R_{2}+..........R_{n}$$
$$n=$$ number of appliances.
Option C is correct.
Question 2
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The resulting magnetic field at the point O due to the current carrying wire shown in the figure:

A
Points out of the page

B
Points into the page

C
Is zero

D
Is the same as due to the segment WX along.

Solution

Here,

The magnetic field at point O,
is zero due to uv,yz
And cancel each other in case of vw,xy,

And the part wx has magnetic field into the plane of paper (by right hand rule)

$$\textbf{Note:}$$right hand rule states that in case of a line current, point the thumb in the
direction of current, and curl your fingers, the direction of curl gives the direction
of magnetic field at any point.

Option $$\textbf B$$ is the correct answer.
Question 3
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A length of wire carries a steady current. It is bent first to form a circular plane coil of one turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre caused by the same current is

A
Quarter of its first value

B
Unaltered

C
Four times of its first value

D
Half of its first value

Solution

Let length of the wire be $$L$$.

Then in first case,
$$L=2\pi R_1$$

$$B_1=\dfrac{\mu_0I}{2R_1}$$

In second case,
$$L=2(2\pi R_2)$$

$$B_2=2\times \dfrac{\mu_0I}{2R_2}$$

And $$R_2=\dfrac{R_1}{2}$$

Or,$$B_2=2\times 2\dfrac{\mu_0I}{2R_1}$$

$$B_2=4B_1$$

Hence Option $$\textbf C$$ is the correct answer.
Question 4
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The line that draws power supply to your house from Street has

A
$$220\sqrt{2}$$ average voltage.

B
220 V average voltage

C
voltage and current Out of phase by $$\pi/2$$

D
voltage and current possibly differing in phase $$\phi$$ such that $$| \phi| < \dfrac{\pi}{2}.$$

Solution

As the line has some resistance $$(R \, \neq \, 0)$$. Also, line that draws power supply has some inductance and capacitance, hence voltage and current differ in phase $$\phi$$ such that $$|\phi| \, < \, \dfrac{\pi}{2}$$.
Question 5
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A charge particle is moving in the direction of a magnetic field.The magnetic force acting on the particle:

A
is in the direction of its velocity

B
is in the direction opposite to its velocity

C
is perpendicular to its velocity

D
is zero

Solution
Question 6
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A DC current flows through a vertical wire in the downward direction. For an observer looking at the wire, the direction of magnetic field at a point between him and the wire is:

A
Upward

B
To the right

C
To the left

D
Downward

Solution

According to Right hand crew rule If current is flow downward than rotation of screw is Clockwise means to the right Therefore observer looking at wire will see the direction of magnetic field to the Right
Option (B) is correct option.
Question 7
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In ______ appliance Fleming Left Hand rule is not used.

A
Electric fan

B
Mixer

C
Computer

D
Electric generator

Solution

$$\bullet$$ Electric fan, mixer and electric generator, there is current and
magnetic field envolves i.e. there is coil and due to current flowing it in
there will be force. So Fleming left hand rule uses in there types of electric appliances.

$$\bullet$$ But in computer there are many electric component and fleming
left hand rule is not used.

Option (C) is correct.
Question 8
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An alternating current is that current which changes regularly its

A
Magnitude

B
Direction

C
Both a and b

D
None of the above

Solution
Question 9
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The shape of a magnetic field lines around a straight current carrying conductor is.......

A
Circular

B
Straight line

C
Curved

D
Parabolic

Solution
Question 10
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A soft bar is inserted inside a current carrying solenoid. The magnetic field inside the solenoid.

A
Will decrease

B
Will incresae

C
Will become zero

D
Will remain the same

Solution

(b) Will increase
If a soft iron bar is inserted inside a current carrying solenoid. The magnetic field inside the solenoid will increase.