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Electric cell - class-VIII

Description: Electric Cell,electric current through conductors
Number of Questions: 17
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Tags: physics electric current through conductors electricity chemical effects of electric current
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Filament of torch bulb is ?

  1. A metal case

  2. Metal tip at the centre of the base

  3. 2 thick wires

  4. Thin wires


Correct Option: D
Explanation:

A filament of a bulb is spirally wounded wire inside the bulb supported by two thick wires at its ends. The filament is wire, which is mostly made up of tungsten. 

As electric current passes through the filament, it glows to produce light.

An inductor coil stores $U$ when a current is passed through it and dissipates heat energy at the rate of $P .$ The time constant of the circuit when this connected across a battery of zero internal resistance is:


  1. $\frac { 4 U } { P }$

  2. $\frac { U } { P }$

  3. $\frac { 2 U } { P }$

  4. $\frac { 2 P } { 6U }$


Correct Option: C

An electric circuit which starts from one terminal of a cell and ends at the other terminal of the cell without any break is called:

  1. open electric circuit

  2. closed electric circuit

  3. complete electric circuit

  4. both b and c


Correct Option: D

Five cells each of emf $\varepsilon $ and internal resistance r each are connected in series. If one cell is connected wrongly, then potential difference across this cell will be

  1. $\dfrac { 8\varepsilon }{ 5 } $

  2. zero

  3. $\dfrac { 4\varepsilon }{ 5 } $

  4. $\dfrac { 2\varepsilon }{ 5 } $


Correct Option: C

State whether given statement is True or False
We use battery cell in our everyday life ?

  1. True

  2. False


Correct Option: A
Explanation:

We use battery cell in everyday life. This statement is true because battery cell is used on daily devices like remotes,Clocks, torch etc.

A wire of length $L$ and $3$ identical cells of negligible internal resistances are connected in series. Due to the current, the temperature of the wire is raised by $\Delta\ T$ in a time $t$. A number $N$ of similar cells is now connected in series with a wire of the same material and cross-section but of length $2\ L$. The temperature of the wire is raised by the same amount $\Delta\ T$ in the same time. The value of $N$ is

  1. $4$

  2. $6$

  3. $8$

  4. $9$


Correct Option: B

Two cells of emf's $3V$ and $3V$ have internal resistances  $1.5\Omega\ &\ 1\Omega$ are connected in parallel across $3\Omega,$ such that they send the current through $3\Omega$ in same direction calculate the p.d. across $3\Omega$ resistor.

  1. 3V

  2. 4V

  3. 1.5V

  4. 2.5V


Correct Option: A

How many cells each marked ( 12V - A) should be connected  in mixed  grouping  so that it may be marked as ( 48 V- 18 A)  

  1. 4

  2. 8

  3. 12

  4. 16


Correct Option: A

Why the bulb brighter in a simple circuit that has more cells?

  1. Because the flow of electricity is more

  2. Because the flow of electricity is same

  3. Because the flow of electricity is less

  4. None of these


Correct Option: A

Two Leclanche cells assisting each other could be balanced on a length $L$ of a potentiometer wire. If the current through the wire is halved, what will be balancing length for one Leclanche cell?

  1. $L/4$

  2. $L/2$

  3. $L$

  4. $2L$


Correct Option: B

The two ends of a copper conductor of length 3.2 cm are connected to a battery acceleration of free electrons is

  1. $ 2 \times 10^{14} ms^{-2} $

  2. $ 3 \times 10^{14} ms^{-2} $

  3. $ 4 \times 10^{14} ms^{-2} $

  4. $ 5 \times 10^{14} ms^{-2} $


Correct Option: A

A cell in which chemical energy is converted into electric energy by first passing a current through it is called a _________.

  1. Primary cell

  2. Secondary cell

  3. Photocell

  4. Electrostatic machine


Correct Option: A
Explanation:

The cell in which chemical energy is converted into electrical energy is called a primary cell. Leclanche cell, Daniel cell, Voltaic cell are all primary cells and not the storage cells.

In torch light cell is used as source of which energy ?

  1. Electrical Energy

  2. Mechanical Energy

  3. Chemical Energy

  4. None of these


Correct Option: A
Explanation:

In torch light, cell is used as a source of electrical energy.

As electrical cell internally converts stored chemical energy into electrical energy, allowing a current to flow from the positive terminal round to the negative one via an external circuit .

Which of the following is the purpose of an electrical cell?

  1. To change mechanical energy to electrical energy

  2. To change chemical energy to electrical energy

  3. To change electrical energy to mechanical energy

  4. To change electrical energy to chemical energy


Correct Option: B
Explanation:

An electrical cell is an "electrical power supply" - internally it converts stored chemical energy into electrical potential energy, allowing a current to flow from the positive terminal round to the negative one via an external circuit (this is called conventional current, which is chosen to go from + to -).

State whether true or false :

Do not connect the two terminals of a cell with a single wire.

  1. True

  2. False


Correct Option: A
Explanation:

We should not connect the two terminals of the cell with a wire without an appliance connected in a circuit. This is because by doing so, chemicals in the cell gets used up quickly and after sometime cell will stop working.

 What are the three basic parts of a cell?

  1. Electrodes, electrolyte, container

  2. Electrodes, acid, water

  3. Anode, cathode, ions

  4. Anode, load, depolarize


Correct Option: A
Explanation:

A cell is basically a source of energy or electrical energy; there are three basic things required to make a cell work.

$i)$ The source of energy,(electrolyte)
$ii)$ The conduction medium to transfer energy (electrodes)
$iii)$ The contained to stare the energy. 

How many different colors of wire are needed to ignite the bulb when connected with cell ?

  1. 2

  2. 1

  3. 4

  4. 6


Correct Option: A
Explanation:

There are two wires needed to connect and ignite the bulb when connected with cell.

$(i)$ To connect the terminal of the cell to the terminal of the bulb.
$(ii)$ The tungsten wire which will get lighten up.
Option $A$ is the correct answer. 

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