1)Which of the following cannot be charged easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woollen cloth
ANSWER:- (b) A copper rod
2)When a glass rod is rubbed with a piece of silk cloth the rod
(a) and the cloth both acquire positive charge.
(b) becomes positively charged while the cloth has a negative
charge.
charge.
(c) and the cloth both acquire negative charge.
(d) becomes negatively charged while the cloth has a positive
charge.
charge.
ANSWER:- (b) The rod becomes positively charged, while the cloth has a
negative charge.
negative charge.
3)Write T against true and F against false in the following
statements.
statements.
(a) Like charges attract each other. (T / F)
(b) A charged glass rod attracts a charged plastic straw. (T /
F)
F)
(c) Lightning conductor cannot protect a building from
lightning. (T/F)
lightning. (T/F)
(d) Earthquakes can be predicted in advance. (T / F)
ANSWER:-
(a) False
(b) True
(c) False
(d) False
4) Sometimes, a crackling sound is heard while taking off a
sweater during winters. Explain.
sweater during winters. Explain.
ANSWER:-When a sweater is taken off, the woollen sweater
gets charged because of the friction between the
sweater and the body. Hence, one can hear a crackling
sound.
gets charged because of the friction between the
sweater and the body. Hence, one can hear a crackling
sound.
5)Explain why a charged body loses its charge if we touch it
with our hand.
with our hand.
ANSWER:-When we touch a charged object, our body
conducts its charges to the earth. That is why a
charged body loses its charge.
conducts its charges to the earth. That is why a
charged body loses its charge.
6)Name the scale on which the destructive energy of an
earthquake is measured. An earthquake measures 3 on this scale. Would it be
recorded by a seismograph? Is it likely to cause much damage?
earthquake is measured. An earthquake measures 3 on this scale. Would it be
recorded by a seismograph? Is it likely to cause much damage?
ANSWER:-The destructive energy of an earthquake is measured by the Richter
scale.
scale.
The reading of magnitude 3 on the Richter scale would be recorded
by a seismograph.
by a seismograph.
If the Richter scale gives a reading of magnitude 3, then the
earthquake is not likely to cause much damage.
earthquake is not likely to cause much damage.
7) Suggest three measures to protect ourselves from lightning.
ANSWER:- (i) Stay in a completely closed place.
ii)Do not bath in running water. This may cause an electric shock.
iii)Do not touch any electrical wires, telephone cables, metal
pipes, etc.
pipes, etc.
8)Explain why a charged balloon is repelled by another charged
balloon whereas an uncharged balloon is attracted by another charged balloon?
balloon whereas an uncharged balloon is attracted by another charged balloon?
ANSWER:-The nature of charges present on the surface of
charged balloons are similar. Since like charges
repel each other, two charged balloons repel each
other. When a charged body is brought near an uncharged body, the uncharged
body acquires charges on its surface caused by the induction of charges. The
charges are of opposite nature in relation to the charged body. Since unlike
charges attract each other, a charged body always
attracts an uncharged body. Hence, an uncharged
balloon is attracted by another charged balloon.
charged balloons are similar. Since like charges
repel each other, two charged balloons repel each
other. When a charged body is brought near an uncharged body, the uncharged
body acquires charges on its surface caused by the induction of charges. The
charges are of opposite nature in relation to the charged body. Since unlike
charges attract each other, a charged body always
attracts an uncharged body. Hence, an uncharged
balloon is attracted by another charged balloon.
9) Describe with the help of a diagram an instrument which can
be used to detect a charged body.
be used to detect a charged body.
ANSWER:- An electroscope can be used to detect whether a body is charged
or not.
or not.
10) List three states in India where earthquakes are more likely
to strike.
to strike.
ANSWER:-The three states in India where earthquakes are
more likely to strike are Jammu and Kashmir, Gujarat,
and Assam.
more likely to strike are Jammu and Kashmir, Gujarat,
and Assam.
11) Suppose you are outside your home and an earthquake strikes.
What precaution would you take to protect yourself?
What precaution would you take to protect yourself?
ANSWER:- Some of the precautions are as follows:
(i) Try to find an open field away from tall buildings,
installations, tall trees, and electric wires and poles.
installations, tall trees, and electric wires and poles.
(ii) If travelling in a bus or a car, then do not come out when an
earthquake strikes.
earthquake strikes.
12)The weather department has predicted that a thunderstorm is
likely to occur on a certain day. Suppose you have to go out on that day. Would
you carry an umbrella? Explain.
likely to occur on a certain day. Suppose you have to go out on that day. Would
you carry an umbrella? Explain.
ANSWER:-No. We should not carry an umbrella in a thunderstorm. During
thunderstorms, which are accompanied
with lightning, electric discharge from the clouds can travel through the
metallic rod of the umbrella.
thunderstorms, which are accompanied
with lightning, electric discharge from the clouds can travel through the
metallic rod of the umbrella.