Balbharati solutions for Science and Technology 9th Standard Maharashtra State Board chapter 3 - Current Electricity [Latest edition]

The accompanying figure shows some electrical appliances connected in a circuit in a house. Answer the following questions.

1. By which method are the appliances connected?
2. What must be the potential difference across individual appliances?
3. Will the current passing through each appliance be the same? Justify your answer.
4. Why are the domestic appliances connected in this way?
5. If the T.V. stops working, will the other appliances also stop working? Explain your answer.

The following figure shows the symbols for components used in the accompanying electrical circuit. Place them at proper places and complete the circuit.

Which law can you prove with the help of above circuit?

Umesh has two bulbs having resistances of 15Ω and 30Ω. He wants to connect them in a circuit, but if he connects them one at a time the filament gets burnt. Answer the following. 

1. Which method should he use to connect the bulbs?
2. What are the characteristics of this way of connecting the bulbs depending on the answer of A above?
3. What will be the effective resistance in the above circuit?

The following table shows the current in Amperes and potential differences in Volts.

1. Find the average resistance.
2. What will be the nature of the graph between the current and potential difference? (Do not draw a graph.)
3. Which law will the graph prove? Explain the law.

Match the pairs.

The resistance of a conductor of length x is r. If its area of cross-section is a, what is its resistivity? What is its unit?

Resistances R_1, R₂, R₃ and R₄ are connected as shown in the figure. S1 and S2 are two keys. Discuss the current flowing in the circuit in the following cases.

1. Both S₁ and S₂ are closed.  
2. Both S₁ and S₂ are open.
3. S₁ is closed but S₂ is open. 

Three resistances x₁, x₂, and x₃ are connected in a circuit in different ways. x is the effective resistance. The properties observed for these different ways of connecting x₁, x₂ and x₃ are given below. Write the way in which they are connected in each case. (I-current, V-potential difference, x-effective resistance) 

1. Current I flows through x₁, x₂ and x₃
2. x is larger than x₁, x₂ and x₃
3. x is smaller than x₁, x₂ and x₃
4. The potential difference across x₁, x₂ and x₃ is the same
5. x = x₁ + x₂ + x₃ 
6. x = `1/(1/X_1 + 1/X_2 + 1/X_3)`

The resistance of a 1m long nichrome wire is 6 ohm. If we reduce the length of the wire to 70 cm. what will its resistance be? 

When two resistors are connected in series, their effective resistance is 80 Ω. When they are connected in parallel, their effective resistance is 20 Ω. What are the values of the two resistances?

If a charge of 420 C flows through a conducting wire in 5 minutes what is the value of the current?