Tag: physics

Questions Related to physics

Out of the following the one which is a source of e.m.f is:

types of cells electricity physics

  1. voltaic cell

  2. dynamo

  3. thermocouple

  4. lous speaker

Show answer
Correct Option: A
Explanation:

A voltaic cell is an electrochemical cell that produces electrical energy. In voltaic cell there is an anode where oxidation occurs and a cathode where reduction occurs. So, it produces current and thus emf is produced in voltaic cells.

For a cell reaction involing a two-electron change, the standard e.m.f of the cell is fonud to be$0.295V$ at $25^{o}C$. The equilibrium constant of the reaction at $25^{o}C$ will be:

types of cells electricity physics

  1. $10$

  2. $1\ \times 10^{10}$

  3. $1\ \times 10^{-10}$

  4. $29.5\ \times 10^{-2}$

Show answer
Correct Option: D

The electric cell is a device to obtain ?

types of cells electricity physics

  1. electric charge

  2. electric force

  3. electrons

  4. electric energy from chemical energy

Show answer
Correct Option: D
Explanation:

It is a common misconception that battery or cell delivers charge but this is not true at all.The battery as a whole is electrically neutral and its only job is to provide electrical energy.This is usually done using conversion of chemical energy to electric energy.

An electrochemical cell stops working after some time because

types of cells electricity physics

  1. Electrode potential of both the electrodes become zero.

  2. Electrode potential of both the electrodes become equal.

  3. One of the electrode is eaten away.

  4. The reaction starts proceeding in opposite direction.

Show answer
Correct Option: A

A $100$ watt, $110$ volt lamp is connected in series with an electrolytic cell containing $CaSO _4$ solution, the weight of Cd deposited by the current for $10$ hrs is (Sl.wt. of Cd=112.4)

types of cells electricity physics

  1. $19.06$g

  2. $38.12$g

  3. $1.906$g

  4. $3.812$g

Show answer
Correct Option: B

In an electric containing battery, the positive charge inside the battery.

types of cells electricity physics

  1. always goes from the positive terminal to the negative terminal

  2. may go from the positive terminal to the negative terminal

  3. always goes from the negative terminal to the positive terminal

  4. May go either side depending on the absolute value of the electric field.

Show answer
Correct Option: D

The power supplied by a battery (or source) is maximum when the external resistance 'R' is equal to the 

types of cells electricity physics

  1. Internal resistance 'r'

  2. Half of the internal resistance 'r'

  3. Two times of initial resistance 'r'

  4. None of these

Show answer
Correct Option: A

A cell of emf E is connected across a resistance r . The potential difference terminals of the cell is found to be V . The internal resistance of the cell must be 

types of cells electricity physics

  1. $\dfrac { \left( E-V \right) V }{ r } $

  2. $\dfrac { 2\left( E-V \right) V }{ r } $

  3. $\dfrac { \left( E-V \right) r }{ V } $

  4. $\left( E-V \right) r$

Show answer
Correct Option: C

A cell drives a current of 1 A in to load of resistance $4W$. On doubling the load resistance. the current is found to be reduced by $40 \%$. The internal resistance of the cell is

types of cells electricity physics

  1. $0.5 W$

  2. $1 W$

  3. $4 W$

  4. $2 W$

Show answer
Correct Option: A

The Zinc rod in leclanche cell is coated with a thin layer of mercury because

types of cells electricity physics

  1. The defect of polarization is removed.

  2. The defect of local action is removed.

  3. The cell does not remain dirty.

  4. The cell is brightened.

Show answer
Correct Option: B
Explanation:

Local Action is the tendency for the chemically active components of a cell to react with each other, and so become exhausted even when no current is being drawn from the cell. Local action has the effect of reducing the 'shelf-life' of the cell - it uses up its chemical reserves and becomes exhausted even when not being used.

In a cell formed from zinc and copper electrodes suspended in a weak acid solution, local action can be seen. The zinc becomes coated with hydrogen bubbles, as a result of its reacting with the acid, even when no current is being drawn. After a while either the zinc will be entirely consumed, or the acid will be neutralised. To avoid this, a thin layer of mercury is coated on zinc rod.