Science chapter4

Answer the following. 

1. On what factors does the electrostatic force between two charges depend? 

The electrostatic force between two charges depend on the following factors :

(i) value of charges on them

(ii) distance between them

(iii) nature of medium between them

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2. What are electric lines of force? 

The lines representing the electric field are called electric lines of force.

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3. Define electric field.

 

Electric field is the region around a charged body within which it can attract (or) repel another charged body.

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4. Define electric current and give its unit. 

1. Electric current is the rate at which charges flow across a conductor in a circuit.

2. The SI unit for current is ampere (A)

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5. State Ohm’s law. 

Ohm's law states that, the current passing through a conductor is directly proportional to the potential difference across its ends, provided the physical conditions like temperature, density, etc. remain unchanged. 

V = IR.

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6. Name any two appliances which work under the principle of heating effect of current

1. Iron box

2. Water heater

3. Toaster

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7. How are the home appliances connected in general, in series or parallel. Give reasons. 

Series circuit

Parallel circuit

Home appliances are connected in parallel because,

1. Each appliances will get the full voltage.

2. The parallel circuit divided the current through the appliances.

3. Each appliances will get the proper current depending on its resistance.

4. Each of them can be put on / off independently.

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8. List the safety features while handling electricity.

Grounding

Trip switch

1. Ground connection

2. Trip switch

3. Fuse

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Conceptual questions. 

1. A bird sitting on a high power electric line is still safe. How? 

1.A bird on a single electric line is safe because no electric circuit is made. 

2.Both feet touch the same wire, meaning there is no voltage difference and no path to the ground.

3.The metal wire is much better at carrying electricity than the small body of a bird. 

Hence the electricity stays in the wire.

4.If a large bird touches two different wires at the same time, the electricity will flow through its body because the wires have different voltage levels

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2. Does a solar cell always maintain the potential across its terminals constant? Discuss. 

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3. Can electroplating be possible with alternating current?

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