In this post, you will get Class 10 Science Chapter 11 Electricity contains solutions of all intext and end exercise questions. These solutions will help the students of class 10 to understand concepts.
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This post covers
complete syllabus and lets you secure the best results in RBSE and other board
exams
Chapter 11- Electricity
Answers of Questions on Page172
Q.1 What does an
electric circuit mean?
Ans.
A continuous and closed path of an electric
current is called an electric circuit.
Q.2 Define the unit of
current.
Ans.
Unit of current is ‘Ampere’, which is
constituted by the flow of one coulomb of charge per second. (Ampere is denoted
by A).
Q.3 Calculate the
number of electrons constituting one coulomb of charge.
Ans.
Answers of Questions on Page174
Q.1 Name a device that
helps to maintain a potential difference across a conductor.
Ans.
A cell or battery helps to maintain a
potential difference across a conductor.
Q.2 What is meant by
saying that the potential difference between two points is 1 V?
Ans.
Potential difference between two points in
a current carrying conductor will be 1 Volt when 1 Joule of work is done to
move a charge of 1 coulomb from one point to the other.
Q.3 How much energy is
given to each Coulomb of charge passing through 6 V battery?
Ans.
Answers of Questions on Page181
Q.1 On what factors do
the resistance of a conductor depends?
Ans.
The resistance of a conductor depends on
(i) Lengths
(ii)
area of cross-section and
(iii) Nature of the material of the conductor.
Q.2 Will current flow
more easily through a thick wire or a thin wire of the same material, when
connected to the same source? Why?
Ans.
Current will flow more easily through a
thick wire of the same material when connected to the same source, because
resistance is the obstruction offered by conductor and it is inversely,
proportional to area of cross-section of the conductor. So a thick conductor
offers lesser resistance than a thin wire.
Q.3 Let the resistance
of an electrical component remains constant while the potential difference
across the two ends of the component decreases to half of its former value.
What change will occur in the current through it?
Ans.
When the potential difference across the
two ends of the component decreases to half of its former value, the value of
current flowing through it will also change to half of former value because
(according to Ohm’s law) V
Q.4 Why are coils of
electric toasters and electric iron made of an alloy rather than a pure metal?
Ans.
The coils of electric toasters and electric
iron made of nichrome. Nichrome is an
alloy of nickel (60%), chromium (12%), manganese (2%) and iron (26%). The alloy
is used because of –
Ø
Resistivity
of an alloy is higher than that of pure metal.
Ø
They have high melting point.
Ø
On
heating they does not oxidise easily.
Q.5 Use the data in
table 12.2 to answer the following:
(a) Which
among iron and mercury is a better conductor?
(b) Which
material is the best conductor?
Ans.
According to table 12.2
(a) Among iron and mercury, iron in a better conductor.
(b) Silver is the best conductor.
Answers of Questions on Page185
Q.1 Draw a schematic
diagram of a circuit consisting of a battery of three cells of 2 V each, a 5 Ωresistor,
an 8 Ω resistor and 12Ω resistor and a plug key, all connected
is series.
Ans.
Q.2 Redraw the circuit
question 1 putting in an ammeter to measure the current through the resistors
and a voltmeter to measure the voltage across the 12 Ω resistor. Note down the
readings in the ammeter and the voltmeter.
Ans.
Answers of Questions on Page188
Q.1 Judge the
equivalent resistance when the following are connected in parallel:
(a) 1Ω and 106.Ω
(b) 1 Ω and 103 Ω and 106Ω
Q.2 An electric lamp of
100Ω, a toaster of resistance 50Ω, and a water filter of resistance 500 Ω are
connected in parallel to a 220 V source. What is the resistance of an electric
iron connected to the same source that takes as much current as all three
appliances, and what is the current through it?
Q.3 What are the
advantages of connecting electrical devices in parallel with the battery
instead of connecting them in series?
Ans.
Electrical devices are connected in
parallel with the battery instead of in series. It is advantageous to provide
same voltage across each appliance and any appliance may be switched on or off
without interference of the other.
Q.4 How can three
resistors of resistances 2Ω, 3Ω and 6Ω be
connected to give a total resistance of (a) 4Ω (b)1Ω.
Q.5 What is (a)
the highest, (b) the lowest total resistance that can be secured by combination
of four coils of resistance 4Ω, 8Ω, 12 Ω and 24Ω.
Ans.
Answers of Questions on Page190
Q.1 Why does the cord
of an electric heater not glow while the heating element does?
Ans.
We know that H = I2Rt, so heat produced when current passes, through a resistor is directly proportional to its resistance. The resistance of electric heater is much higher than that of coil and it becomes hot and glows.
Q.2 Compute the heat
generated while transferring 96000 Coulomb of charge in one hour through a
potential difference of 50 V.
Ans.
Q.3 An electric iron of resistance 20 Ω takes a current of 5A. Calculate the heat developed in 30 s.
Ans.
Answers of Questions on Page192
Q.1 What determines the
rate at which energy is delivered by a current?
Ans.
Electric power determines the rate at which
energy is delivered by a current.
Q.2 An electric motor
takes 5 A from a 220 V line. Determine the power of the motor and the energy
command in
2h.
Answer
Answers of End Exercise Questions
Q.1 A piece of wire of
resistance R is cut into five equal parts. These parts are then connected in
parallel. If the equivalent resistance of this combination is R’ then the ratio
(a)
(b)
(c) 5
(d) 25
Answer (d)
Q.2 Which of the
following terms does not represent electrical power in a circuit?
(a) I2R
(b) IR2
(c) VI
(d)
Answer (d) IR2
Q.3 An electric bulb is
rated 220 V and 100 W. When it is
operated on 110 V, the power consumed will be:
(a) 100 W
(b) 75 W
(c) 50 W
(d) 25 W
Answer (d) 25
W
Q.4 Two conducting
wires of the same material and of equal lengths and equal diameters are first
connected in series and then parallel in an electric circuit. The ratio of heat
produced in series and parallel combinations would be
(a) 1 : 2
(b) 2
: 1
(c) 1 : 4
(d) 4 : 1
Answer (d) 4
: 1
Q5 How is a voltmeter
connected in the circuit to measure the potential difference between two
points?
Answer
A
voltmeter is connected in parallel to the conductor to find the potential
difference between two points.
Q.6 A copper wire has
diameter has 0.5 mm and resistivity of 1.6 × 10-8
Answer
Q.7 The values of
current I-flowing in a given resistor for the corresponding values of potential
difference V-across the resistor are given below:
Q.8 When a 12 V battery
is connected across an unknown resistor, there is a current of 2.5 mA in the
circuit. Find the value of the resistance of the resistor.
Answer
Q.9 A battery of 9 V is
connected in series with resistors of 0.2Ω, 0.3Ω, 0.4Ω, 0.5Ω, and 12Ω
respectively. How much current would flow through the 12Ω resistor?
Answer
Q.10How many 176 Ω
resistors (in parallel) are required to carry 5 A on a 220 V line?
Answer
Q.11 Show how you
would connect three resistors, each of resistance 6Ω, so that the combination
has a resistance of (i) 9Ω, (ii) 4Ω.
Answer
Q.12 Several
electric bulbs designed to be used on a 220 V electric supply line, are rated
10 W. How many lamps can be connected in parallel with each other across the
two wires of 220 V line if the maximum allowable current is 5 A?
Answer
Q.13 A hot plate of
an electric oven connected to a 220 V line has two resistance coils A and B,
each of 24 Ω resistance, which may be used separately, in series, or in
parallel. What are the currents in the three cases?
Answer
Q.14 Compare the
power used in the 2Ω resistor in each of
the following circuits : (i) 6 V battery in series with 1Ω and 2Ω
resistors, and (ii) a 4 V battery in parallel with 12 Ω and 2Ω resistors.
Answer
Q.15Two lamps, one
rated 100 W at 220 V and the other 60 W at 220 V are connected in parallel to a
220 V supply. What current is drawn from the supply line?
Answer
Q.16Which uses more
energy a 250 W TV set in 1 hour or a 1200 W toaster in 10 minutes?
Answer
Q.17 An electric
heater of resistance 8 Ω draws 15 A from the service mains 2 hours. Calculate
the rate at which heat is developed in
the heater.
Answer
Q.18 Explain the following:
(a) Why is the tungsten used almost exclusively
for filament of electric lamps?
(b) Why are the conductors of electric heating
devices, such as bread-toasters and electric irons, made of an alloy rather
than a pure metal?
(c) Why is the series arrangement not used for
domestic circuits?
(d) How does the resistance of a wire vary with
its area of cross-section?
(e) Why are copper and aluminum wires usually
employed for electricity transmission?
Answer
(a) Tungsten
is used almost exclusively for filament of electric lamps, because it is not
oxidized at high temperature. It has melting point 3380
(b) The conductor of electric heating devices as
toasters and electric irons are made of an alloy rather than a pure metal
because resistivity of an alloy is generally higher than that of pure metals.
(c) In series arrangement the resistance of the
combination of resistors (of used devices) is the sum of the individual
resistors. So series arrangement is not used in domestic circuits.
(d) Resistance of a given wire is the obstruction
offered by conductor. When a battery is connected to the two ends of a
conductor, a potential difference is set up and electrons are accelerated and
move. In their motion they collide with atoms of the conductor. So if area to
pass the electrons is less, obstruction is more and if area is more the
obstruction is less and resistance is less.
(e) Copper and aluminium wire are usually employed
for the transmission of electricity, because their resistivity is very low and
they are good conductor of electricity.
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