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Science [ 2 Marks Questions ]

T2 CH2 Electricity · Tamil Nadu Board STD 7 (Tamil - English Medium). 16 questions.

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[ 2 Marks Questions ]

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16 questions · timed · auto-graded

Question 12 Marks
Higher Order Question
A student made a circuit by using an electric cell, a switch, a torch bulb (fitted in the bulb holder), and copper connecting wires. When he turned on the switch, the torch bulb did not glow at all. The student checked the circuit and found that all the wire connections were tight.
  • What could be the possible reason for the torch bulb not glowing even when the circuit appears to be complete?
Answer
The possible reasons so that even at switch ‘ON’ position the bulb is not glowing are:
  1. The cell may be discharge
  2. The bulb may be fused.
  3. The wire may be broken from inside
  4. The connection may be loose.
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Question 22 Marks
Observe the circuit given:
1.Would any of the bulb glow when the switch is in the ‘OFF’ position?
Image
2.What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?
Answer
  1. No bulb will glow
  2. All bulbs will glow simultaneously.
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Question 32 Marks
What is the difference between fuse wire and a heating wire?
Answer
The fuse wire has low melting point, whereas the heating wire has a high melting point. Fuse wire is made up of tin-lead alloy, whereas heating wire is made of constant. (Copper and nickel alloy)
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Question 42 Marks
If $3A$ current flows through a circuit, then convert the current in terms of milliampere.
Answer
$I=3 A $
$ 1 A =103 mA$
$ 3 A =3 \times 1000 mA $
$ 3 A =3000 mA$
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Question 52 Marks
If $5A$ current flows through a circuit, then convert the current is terms of micro ampere?
Answer
$I=5 A$
$ I A=106 \mu A $
$ 5 A=5 \times 106 \mu A$
$5 A=50,00,000 \mu A$
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Question 62 Marks
If 50 coulomb of electric charge flows through a wire in five minutes, calculate the current in the wire?
Answer
Charge $q =50 C$
time $t =5 min \times 60 s =300 s$
current $I =\frac{q}{t}$
$
=\frac{50}{300}=\frac{5}{30}=0.166 A
$
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Question 72 Marks
What are the factors affecting heating effect of electric current?
Answer
  1. The amount of current I.
  2. The resistance R and
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Question 82 Marks
Write the analogy between water current and electric current.
Answer
  1. Water molecules flow towards a point of lower elevation.
  2. Electric charges flow towards a point of lower voltage.
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Question 92 Marks
What do you mean by an open circuit?
Answer
Image
An open circuit occurs when there is break in the circuit which stops the current from flowing. Breaks in the circuit can be due to many causes, such as loose bulb holder or a missing wire in the circuit.
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Question 102 Marks
Define electric cell. What is the direction of electric current in a cell?
Answer
  1. The simplest sources of an electric current is an electric cell and it has a positive terminal and a negative terminal.
  2. In electric cell the current starts from positive terminal of the cell, passes through the equipment connected to it, and terminates at the negative terminal of the cell.
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Question 112 Marks
What is heating effect of the electric current?
Answer
  1. The wire or component gets hot when an electric current passes through them,
  2. This is known as heating effect of the electric current.
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Question 122 Marks
What are MCB’s? How do they work?
Answer
  1. MCB’s (Miniature Circuit Breakers) are switches which automatically turn off when current in a circuit exceeds the safe limit.
  2. We turn them on and the circuit is once again complete.
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Question 132 Marks
What do you mean by magnetic effect?
Answer
When electric current passes through a wire, it behaves like a magnet. This is called magnetic effect of electricity.
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Question 142 Marks
What is an electric fuse made up of?
Answer
A fuse is a small place of wire of an alloy of low melting point (63% tin and 37% lead).
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Question 152 Marks
What are the uses of electromagnets?
Answer
Electromagnets are used in cars, speakers, electric motors, electric cells, telephone receivers and television.
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Question 162 Marks
What is resistance?
Answer
Resistance is the property of an electrical component which resists the flow of electric charges, when it is connected is a circuit.
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[ 2 Marks Questions ] - Science STD 7 Questions - Vidyadip