Chapter 12 – electricity and circuit
ACTIVITY-1: To
observe the filament of bulb and its functions.
Question 1- The
part of bulb which produces light is called _________.
Answer- Filament.
Question 2- The
electric bulb has _______ terminals.
Answer- Two.
ACTIVITY- 3: To
make a switch.
Question 1-
What is the function of electric switch?
Answer- Electric switch is used to start (ON) or stop
(OFF) the flow of electric current in a circuit.
Question 2- In
an electric circuit the circuit break when switch is in _______ position.
Answer- OFF.
EXERCISE
Question 1- Fill In
The Blanks.
a). A device that is used to break or make an electric
circuit is called switch.
b). An electric bulb glows when electric current flows through it.
c). Conductors
are materials through which electric current can pass.
d). Current cannot pass through insulators.
Question 2- Write
True Or False.
a). Electric current can flow through metals. (True)
b). Instead of metal wires, a jute string can be used
to make a circuit. (False)
c). Electric current can pass through a pencil lead. (True)
d). When chemicals in dry cell are used up, it stops
working. (True)
e). LED based lamps are eco-friendly. (True)
Question 3- Match
The Column:-
|
1.
Button cell |
|
|
2.
Dry cell |
|
|
3.
LED bulb. |
|
|
4.
Electric switch |
|
Question 4. Choose
The Correct Answer.
(i). Battery is
a combination of:
a) Conductors
b) Insulators
c) Electric cells (✓)
d) Filaments
(ii). The basic
electric circuit needs to have:
a) Only a source of electric current
b) Only a few conducting wires
c) Only a device or appliance
d) All the above (✓)
(iii). On
passing current through an electric bulb, bulb starts emitting light because its:
a) Filament starts emitting light and then gets heated
up
b) Thick connecting wires start emitting light and
then get heated up
c) Filament gets heated up and then starts emitting
light (✓)
d) Thick wires get heated up and then starts emitting
light
Question 5- Very
Short Answer Type Questions.
(i) What is
electric cell?
Answer- Electric cell is a source of electric current.
(ii) What is
electric current?
Answer- Electric current is the rate of flow of
electric charge in a conductor.
(iii) What is
electric circuit?
Answer- Electric circuit is an arrangement of battery,
switch, electric device and conducting wires, which provides a complete path
for electricity to pass.
Question 6- Short
Answer Type Questions.
(i) Tools like
screw drivers and pliers used by electricians have handles made up of plastic, rubber, wood. Why?
Answer- Because plastic and rubber are insulators. So
it protects the electrician from the shock of electricity.
(ii) Why should
we dry our hands before touching an electric appliance or a switch?
Answer- Because normal water is conductor of
electricity, so with wet hands we can get electric shock.
(iii) A student
while performing an experiment in the science lab, connected an electric bulb
to an electric cell through an electric switch. He noticed that the bulb does
not glow when the electric switch was set in its ON position. Mention ant two
reasons for this observation.
Answer- (1) Electric switch may be faulty,
(2) Connections may be loose,
(3) Electric cell may be used up.
(iv)
Distinguish between the terms conductors and insulators of electricity. Give two examples of each type.
Answer-
|
Conductors |
Insulators |
|
1.
Conductors are materials through which electric current can pass. |
1.
Insulators are materials through which electric current cannot pass. |
|
2.
Examples: Metals- Iron, copper, aluminium etc. |
2.
Examples: All non-metals except graphite, rubber, plastic, wood etc. |
(v) Explain why the bulb would not glow in the
arrangement shown at below:
Answer- Bulb will not glow in the arrangement because
the handle of the tester used in the connection is made of plastic which is an
insulator.
(vi) Match the labels with the correct parts of the
circuit given below:
Provides
Electric Current
A Device used for Making/ Breaking a Circuit
Device which
Lights up
Answer:-
Question 7- Long
Answer Type Questions.
(i) Using the
“conduction testes” on an object it was found that the bulb begins to glow. Is that object conductor
or insulator? Explain.
Answer- That object is conductor, because conductors
allow to pass electricity through it. So circuit gets completed and bulb glows.
(ii) The
handles of the tools like screw drivers and pliers used by electricians for repair work usually have plastic
or rubber covers on them. Can you explain why?
Answer- Because plastic and rubber are insulators. So
it protects the electrician from the shock of electricity.
