NCERT Class VII Science Solutions: Chapter 14-Electric Current and its Effects Part 2

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Question 4:

The bulb in the circuit shown in Fig.14.23 does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.

Changes in the circuit to make the bulb glow (Q)

Changes in the Circuit to Make the Bulb Glow (Q)

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Answer:

The positive terminal (+) of one cell always be connected to negative terminal (-) of another cell. Here the two positive terminals are connected to each other. The correct arrangement is as follows:

Images for The correct arrangement is as follows

The Correct Arrangement is as Follows

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Question 5:

Name any two effects of electric current.

Answer:

Heating Effect of current:

  • When an electric current passes through a wire, the wire gets heated. This is known as the heating effect of current which is used in many heating applications like electric heater, electric ion, light bulb etc.

This diagram shows heating effect of current

Heating Effect of Current

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Magnetic Effect of current:

  • When an electric current flows through a wire, it generates magnetic field around it. This effect is called magnetic effect of current. Magnetic Effect of electric current has many applications like power lift, electric bell, electric fan etc.

Images for Magnetic effect of current

Magnetic Effect of Current

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Question 6:

When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.

Answer:

The current carrying wire produces magnetic field around it. When a compass is kept nearby this wire, the two magnetic field (magnetic field due to wire and magnetic field due to compass) interact each other causing deflection in magnetic needle. When the current is switched off, there is no magnetic field produced by the wire, magnetic needle does not deflect from its north-south position.

As showing in images is a result for a compass

Result for a Compass

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