Electric Current and its Effects Test

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Electric Current and its Effects Test - 15

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Weekly Quiz Competition

Question 1
1 / -0

What happens when the electromagnet pulls the iron strip in an electric bell?

A
It completes the circuit

B
It breaks the circuit

C
The current stops flowing

D
Both $$B$$ & $$C$$

Solution

In an electric bell,when the electromagnet pulls the iron strip, it breaks the circuit because that iron strip was part of the circuit.Since current only flows in closed circuits,the current through the coil stops flowing, thus option $$D$$ is correct
Question 2
1 / -0

There is a _______ limit on the current which can safely flow through a ________

A
Minimum, building

B
Maximum, building

C
Minimum, circuit

D
Maximum, circuit
Question 3
1 / -0

Which of the following is the reason for overflow of current in circuits?

A
The direct touching of wires

B
Connection of many devices to a single socket

C
Using a fuse

D
Both $$A$$ & $$B$$

Solution

Reasons for excessive currents in
electrical circuits are the direct
touching of wires and the
connection of many devices to a single
socket, hence option $$D$$ is correct.
Question 4
1 / -0

When is the circuit complete of an electric bell?

A
When the iron strip touches the contact screw

B
When the iron strip is no longer attracted by the coil

C
When the hammer doesn't strike the gong

D
When the bell no longer rings

Solution

When the
iron strip comes back to its original
position and touches the contact screw
again, it completes the circuit, thus option $$A$$ is correct.
Question 5
1 / -0

Which of the following is not a function of a fuse?

A
Blowing off and breaking the circuit

B
Preventing damages to electrical circuits

C
Preventing possible fires

D
Glowing

Solution

A fuse is a safety device which prevents damages to electrical circuits and possible fires by blowing off and breaking the circuit,when currect exceeds a maximum value. Fuse does not glow .Hence option $$D$$ is correct.
Question 6
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Take an electric cell, a bulb, a switch and connecting wires. Make an electric circuit as shown in this figure above. This activity has to be done using only one cell. Keep the switch in the OFF position and touch the bulb. What do you feel?

A
The bulb is slightly warm to touch

B
The bulb is extremely cold to touch

C
The bulb is very hot

D
The bulb is at normal temperature

Solution

$$\textbf{Concept applied:}$$ Heating Effect of Electric Current

$$\textbf{Correct option: D}$$

$$\textbf{Explanation:}$$
$$\bullet$$ Since the switch is kept in an 'OFF' position, the circuit does not form a closed path. We know current only flows in a closed circuit. So NO current will flow in the circuit.
$$\bullet$$ According to the heating effect of electric current, the CURRENT flowing through an element produces HEAT.
$$\bullet$$ Since no current is flowing in the bulb, NO heat will be generated, and the bulb will remain at its Normal Temperature.
Question 7
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Make a circuit as shown in the figure above. Take about $$10\ cm$$ long piece of nichrome wire and tie it between the nails. (You can get nichrome wire from an electric repair shop or you can use a piece of a discarded coil of an electric heater.) Touch the wire. Now switch on the current in the circuit by moving the switch to the ‘ON’ position. After a few seconds touch the wire. What difference do you observe?

A
No difference

B
The wire becomes very hot

C
The wire becomes cold

D
The wire is slightly warm to touch

Solution

When an electric current flows through the nichrome wire, the wire gets heated. It is the heating effect of current.
Question 8
1 / -0

Consider $$A$$ & $$B$$, which of these demonstrates heating effects of electric current?

A
$$A$$

B
$$B$$

C
Both of these

D
None of these

Solution

$$\textbf{Concept to be used:}$$
$$\bullet$$ Heating effect of current

$$\textbf{Correct Option: A}$$

$$\textbf{Explanation for Correct option:}$$
$$\bullet$$ The heating effect of electric current is utilised in devices such as electric heater, electric iron etc.
$$\bullet$$ When the electric circuit is purely resistive, that is, a configuration of resistors only connected to a battery; the source energy continually gets dissipated entirely in the form of heat.
$$\bullet$$ The heat is produced in the heating coil of the electric iron given by Joule's law of heating, $$H=I^2Rt.$$

$$\textbf{Explanation for Incorrect option:}$$
Any option containing the case $$B$$ will be incorrect because it demonstrates the magnetic effects of current. So option $$B$$ and $$C$$ are incorrect.
Option $$D$$ is also becomes incorrect because option $$A$$ is correct.
Question 9
1 / -0

Take an electric cell, a bulb, a switch, and connecting wires. Make an electric circuit as shown in the figure above. This activity has to be done using only one cell. Move the electric switch to the ‘ON’ position and let the bulb glow for a minute or so. Touch the bulb. What do you feel?

A
The bulb is slightly warm to touch

B
The bulb is very hot

C
The bulb is extremely cold to touch

D
The bulb is normal temperature

Solution

$$\textbf{Concept applied:}$$ Heating Effect of Electric Current

$$\textbf{Correct option: A}$$

$$\textbf{Explanation for correct option:}$$
$$\bullet$$ When the switch is ON, the bulb is connected to the circuit, and electric current flows through the bulb.
$$\bullet$$ Due to the heating effect of electric current, the temperature of the bulb rises, but as the time duration of current flow is just a minute, temperature rises slightly.
$$\bullet$$ Hence, the bulb is slightly warm to touch.

$$\textbf{Explanation for incorrect options:}$$
$$B:$$ Since the time duration of current flow was not long, the bulb cannot be very hot.
$$C:$$ Electric current generates heat while flowing through a circuit element. Hence the bulb can't be cold.
$$D:$$ Electric current generates heat while flowing through a circuit element. Hence the bulb can't be of normal temperature.
Question 10
1 / -0

Look at the circuit diagram above and choose the correct option.

A
The bulb will glow and turn cold

B
The bulb will glow and turn extremely hot

C
The bulb not glow but turn hot

D
The bulb will neither glow nor turn hot or cold

Solution

$$Concept\ to\ be\ used :$$
Heating effect of electric current : When a current $$I$$ is passed through a conductor of resistance $$R$$ for a time $$t$$, the heat produce in it, $$H=I^2Rt$$

$$Corret \ option : D$$

$$Explanation :$$
$$\bullet$$ Since the switch is kept in an 'OFF' position, the circuit does not form a closed path, and the current only flows in a closed circuit. So no current will flow and the bulb will not glow.
$$\bullet$$ According to the heating effect of electric current, the current flowing through an element produces heat.
$$\bullet$$ Since no current is flowing in the above circuit, so no heating effect will be there and the bulb will remain at the normal temperature. It will neither be hot nor cold.