HARD
7th CBSE
IMPORTANT
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Rekha was ironing her dresses. Suddenly, there were some sparks near the socket ans the electric iron's cable started to burn. Why does it happen? What is the reason behind the cord catching fire?

Important Questions on Electric Current and Its Effects

HARD
7th CBSE
IMPORTANT

Dinesh wanted to buy and electric bell for his front door. He asked his friends for their opinions. Some suggested electric doorbell whereas a majority of the other suggested battery operated doorbell. Can you guess the reason why majority of his friends suggested battery operated doorbells?

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HARD
7th CBSE
IMPORTANT

Study this electrical circuit. It consists of a powerful battery, a bulb, an electromagnet and a movable connection. The connection is designed in such a way that it closes (that is, it allows electric current to pass) when the electromagnet is not magnetised; but opens when the electromagnet is magnetised. If the electromagnet takes 5 seconds to get magnetised, what will be status of the electric bulb?

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HARD
7th CBSE
IMPORTANT

See the circuit shown below in figure P. If the battery is connected the other way (as shown in figure Q), what will happen?

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HARD
7th CBSE
IMPORTANT

The diagram shows a flashlight battery and a bulb connected by wires to various substances. Which of the bulbs will light?

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HARD
7th CBSE
IMPORTANT

Many electrical devices like televisions and electric irons have plugs which have 3 pins. However, other devices sometimes work with only 2 pins. Why is the third pin necessary?

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HARD
7th CBSE
IMPORTANT

When connected as shown, the bulb glows, but dimly. Which of these CAN be the explanation for this:

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HARD
7th CBSE
IMPORTANT

Instead of a soft iron core, if we wind a current-carrying wire around a wooden pencil, would it still deflect a magnetic compass needle?

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HARD
7th CBSE
IMPORTANT

The following diagram shows four circuits A, B, C and D. Each circuit has a cell and a torch bulb. Name the circuits in which the bulb will glow? Give reason to your answer

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