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PHYSICS [1 Mark Question Answer]

Current Electricity · ICSE STD 9 (ICSE - English Medium). 25 questions.

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[1 Mark Question Answer]

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25 questions · timed · auto-graded

Question 11 Mark
Which of the following device is most efficient for the lighting purpose? LED, CFL, fluorescent tube light, Electric bulb.
Answer
LED or light emitting diodes are most efficient for lighting purposes.
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Question 21 Mark
What is meant by the efficient use of energy?
Answer
Efficient use of energy means to reduce cost and amount of energy to be used to provide us the various products and services.
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Question 31 Mark
What do you understand by the term resistance?
Answer
The obstruction offered to the flow of current by the filament or wire is called its electrical resistance.
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Question 41 Mark
How is the direction of flow of current between the two charged conductors determined by their potentials?
Answer
Current always flows from high potential to low potential.
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Question 51 Mark
In transferring 1.5 C charge through a wire, 9 J of work is needed. Find the potential difference across the wire.
Answer
Potential difference $(V)=\frac{\text { work done }(W)}{\text { charge }(q)}$
Or, $V=\frac{9}{1.5}=6$ volt.
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Question 101 Mark
State whether the resistance of filament of a bulb will decrease, remain unchanged or increase when it glows.
Answer
The temperature of the filament increases when it glows. So, when the temperature of the wire (bulb filament) increases, ions in it vibrate violently. As a result, the number of collisions increases and hence the resistance increases.
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Question 111 Mark
'The resistance of a wire is 1 ohm'. Explain the meaning of this statement.
Answer
The resistance of a wire is 1 ohm; it means a current of 1 ampere will flow through the wire when the potential difference across it is 1 volt.
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Question 121 Mark
How are the potential difference (V), current (l) and resistance (R) related? 
Answer
Potential difference = Current x Resistance
i.e., V = I R
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Question 131 Mark
Name the constituents of a cell.
Answer
Constituents of cell: Two electrodes and an electrolyte in a vessel.
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Question 141 Mark
What transformation of energy takes place when current is drawn from a cell?
Answer
Chemical energy changes into electrical energy.
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Question 151 Mark
When starter motor of a car is switched on for 0.8 s . a charge 24 C passes through the coil of the motor . Calculate the current in the coil .
Answer
Current $( l )=\frac{\text { Charge }( q )}{\text { time }( t )}$ Or, $I =\frac{24}{0.8}=30 A$
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Question 161 Mark
What is an electric cell?
Answer
An electric cell is a device which converts chemical energy into electrical energy. When connected in a circuit, it acts as a source of D.C. current.
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Question 171 Mark
A current of 1.5 A flows through a conductor for 2.0 s . What amount of charge passes through the conductor ?
Answer
Charge $(q)=$ Current $( l ) \times$ time $( t )$ Or, $q =1.5 \times 2=3 C$
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Question 181 Mark
Write the condition required for a circuit to be a closed circuit.
Answer
For an electric circuit to be closed, every part of it must be made of conductors.
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Question 191 Mark
A charge 0.5 C passes through a cross section of a conductor in 5 s . Find the current .
Answer
Current $( l )=\frac{\text { Charge }( q )}{\text { time }( t )}$ Or, $I =\frac{0.5}{5}=0.1 A$
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Question 211 Mark
Select conductors of electricity from the following: Copper wire, silk thread, pure water, acidulated water, human body, glass, mercury.
Answer
Copper wire, acidulated water and human body and mercury.
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Question 221 Mark
What is the function of a  key (or switch) in an electric circuit?
Answer
A kay or switch is used to put on or off, the current in the circuit.
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Question 231 Mark
Name the instrument used to control the current in an electric circuit.
Answer
A rheostat is used to control current in an electric circuit.
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Question 241 Mark
n electrons flow through a cross section of a conductor in time t. If charge on an electron is e, then write an expression for the current in the conductor.
Answer
Current, $I =\frac{ ne }{ t }$
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[1 Mark Question Answer] - PHYSICS STD 9 Questions - Vidyadip