physics - electricity

Class 10 - Physics

Electricity

MCQ
Q&A
Question:

An electric bulb of resistance 20 Ω and a resistance wire of 4 Ω are connected in series with a 6 V battery. Draw the circuit diagram and calculate :
(a) total resistance of the circuit.
(b) current through the circuit.
(c) potential difference across the electric bulb.
(d) potential difference across the resistance wire.

Answer:

lakhmir singh physics class 10 online Chapter 1 Electricity Q15 Page 38



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Questions and Answers


Electricity - Questions
1.

A student made an electric circuit shown here to measure the current through two lamps.
(a) Are the lamps in series or parallel ?
(b) The student has made a mistake in this circuit.
What is the mistake ?
(c) Draw a circuit diagram to show the correct way to connect the circuit.
Use the proper circuit symbols in your diagram.
lakhmir-singh-physics-class-10-solutions-electricity-2


Answer
2.

Keeping the resistance constant, the potential difference applied across the ends of a component is halved. By how much does the current change ?


Answer
3.

Fill in the following blank with a suitable word :
Ohm’s law states a relation between potential difference and……………………


Answer
4.

What is Ohm’s law ? Explain how it is used to define the unit of resistance.


Answer
5.

Name the material which is used for making the heating element of an electric iron.


Answer
6.

Will current flow more easily through a thick wire or a thin wire of the same material when connected to the same source ? Give reason for your answer.


Answer
7.

The electrical resistivities of four materials A, B, C and D are given below :
Untitled
Which material is : (a) good conductor (b) resistor (c) insulator, and (d) semiconductor ?


Answer
8.

Two resistors, with resistances 5 Ω and 10 Ω respectively are to be connected to a battery of emf 6 V so as to obtain :
(i) minimum current flowing (ii) maximum current flowing
(a) How will you connect the resistances in each case ? .
(b) Calculate the strength of the total current in the circuit in the two cases.


Answer
9.

What is the SI unit of potential difference ?


Answer
10.

If 20 C of charge pass a point in a circuit in 1 s, what current is flowing ?


Answer
11.

Name the law which relates the current in a conductor to the potential difference across its ends.


Answer
12.

A current of 5 amperes flows through a wire whose ends are at a potential difference of 3 volts. Calculate the resistance of the wire.


Answer
13.

What would be the effect on the resistance of a metal wire of :
(a) increasing its length ?
(b) increasing its diameter ?
(c) increasing its temperature ?


Answer
14.

The electrical resistivities of three materials P, Q and R are given below :
Untitled
Which material will you use for making (a) electric wires (b) handle for soldering iron, and (c) solar cells ? Give reasons for your choices.


Answer
15.

Give the law of combination of resistances in series.


Answer
16.

If five resistances, each of value 0.2 ohm, are connected in series, what will be the resultant resistance ?


Answer
17.

How should the two resistances of 2 ohms each be connencted so as to produce an equivalent resistance of 1 ohm ?


Answer
18.

What is the unit of electric charge ?


Answer
19.

Which of the two is connected in series : ammeter or voltmeter ?


Answer
20.

A current of 4 A flows around a circuit for 10 s. How much charge flows past a point in the circuit in this time ?


Answer
21.

State the factors on which the strength of electric current flowing in a given conductor depends.


Answer
22.

On what factors does the resistance of a conductor depend ?


Answer
23.

What is nichrome ? State its one use.


Answer
24.

Why are the coils of electric irons and electric toasters made of an alloy rather than a pure metal ?


Answer
25.

How does the resistance of a wire change when :
(i) its length is tripled ?
(ii) its diameter is tripled ?
(in) its material is changed to one whose resistivity is three times ?


Answer
26.

The electrical resistivities of five substances A, B, C, D and E are given below :
A 5.20 x l0-8 Ω m


Answer
27.

Which of the following resistor arrangement, A or B, has the lower combined resistance ?
lakhmir-singh-physics-class-10-solutions-electricity-38(9)


Answer
28.

A wire that has resistance R is cut into two equal pieces. The two parts are joined in parallel. What is the resistance of the combination ?


Answer
29.

Calculate the combined resistance in each case :
lakhmir-singh-physics-class-10-solutions-electricity-38(11)


Answer
30.

A battery of 9 V is connected in series with resistors of 0.2 Ω, 0.3 Ω, 0.4 Ω, 0.5 Ω and 12 Ω. How much current would flow through the 12 Ω resistor ?


Answer
31.

Which of the following statements correctly defines a volt ?
(a) a volt is a joule per ampere.
(b) a volt is a joule per coulomb.


Answer
32.

(a) What do the letters p.d. stand for ?
(b) Which device is used to measure p.d. ?


Answer
33.

What do you understand by the term “electric potential” ? (or potential) at a point ? What is the unit of electric potential ?


Answer
34.

(a) Name a device that helps to measure the potential difference across a conductor.
(b) How much energy is transferred by a 12 V power supply to each coulomb of charge which it moves around a circuit ?


Answer
35.

What actually travels through the wires when you switch on a light ?


Answer
36.

(a) In which direction does conventional current flow around a circuit ?
(b) In which direction do electrons flow ?


Answer
37.

Which of the following equation shows the correct relationship between electrical units ?
1 A = 1 C/s or 1 C = 1 A/s


Answer
38.

What is the unit of electric current ?


Answer
39.

What do the following symbols mean in circuit diagrams ?
lakhmir-singh-physics-class-10-solutions-electricity-1


Answer
40.

What is an ammeter ? How is it connected in a circuit ? Draw a diagram to illustrate your answer.


Answer
41.

An electric heater is connected to the 230 V mains supply. A current of 8 A flows through the heater.
(a) How much charge flows around the circuit each second ?
(b) How much energy is transferred to the heater each second ?


Answer
42.

How many electrons are flowing per second past a point in a circuit in which there is a current of 5 amp ?


Answer
43.

Keeping the potential difference constant, the resistance of a circuit is halved. By how much does the current change ?


Answer
44.

Distinguish between good conductors, resistors and insulators. Name two good conductors, two resistors and two insulators.


Answer
45.

Name the material which is the best conductor of electricity.


Answer
46.

Why are copper and aluminium wires usually used for electricity transmission ?


Answer
47.

Give two reasons why nichrome alloy is used for making the heating elements of electrical appliances.


Answer
48.

Fill in the following blanks with suitable words :
Resistance is measured in…………….. The resistance of a wire increases as the length…………………. ; as the
temperature………. ; and as the cross-sectional area…………


Answer
49.

How does the resistance of a conductor depend on :
(a) length of the conductor ?
(b) area of cross-section of the conductor ?
(c) temperature of the conductor ?


Answer
50.

How does the resistance of a wire vary with its :
(a) area of cross-section ?
(b) diameter ?


Answer