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Multiple choice types of cells electricity physics

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

  1. voltaic cell

  2. dynamo

  3. thermocouple

  4. lous speaker
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

Multiple choice types of cells electricity physics

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:

  1. $10$
  2. $1\ \times 10^{10}$
  3. $1\ \times 10^{-10}$
  4. $29.5\ \times 10^{-2}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Multiple choice types of cells electricity physics

The electric cell is a device to obtain ?

  1. electric charge

  2. electric force

  3. electrons

  4. electric energy from chemical energy
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

Multiple choice types of cells electricity physics

An electrochemical cell stops working after some time because

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice types of cells electricity physics

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)

  1. $19.06$g
  2. $38.12$g
  3. $1.906$g
  4. $3.812$g
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice types of cells electricity physics

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

  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.
Reveal answer Fill a bubble to check yourself
D Correct answer
Multiple choice types of cells electricity physics

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

  1. Internal resistance 'r'

  2. Half of the internal resistance 'r'

  3. Two times of initial resistance 'r'

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to the Maximum Power Transfer Theorem, the power delivered to an external load is maximized when the load resistance equals the internal resistance of the source. This is derived by setting the derivative of power with respect to R to zero.

Multiple choice types of cells electricity physics

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 

  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. $\left( E-V \right) r$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The terminal voltage V is given by V = E - Ir, where I = V/r_ext. Substituting I, we get V = E - (V/r_ext) * r_int. Rearranging for r_int gives r_int = (E - V) * r_ext / V. The provided options use 'r' as the external resistance.

Multiple choice types of cells electricity physics

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

  1. $0.5 W$
  2. $1 W$
  3. $4 W$
  4. $2 W$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice types of cells electricity physics

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

  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.
Reveal answer Fill a bubble to check yourself
B Correct answer
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.