Chemistry · Physics

Electrochemistry and Current Electricity

272 Questions

Review fundamental concepts of electrochemistry and current electricity through these practice questions. The set includes numerical problems on electrolysis, drift velocity, and electrode potentials. These topics frequently appear in engineering, CSIR NET, and state PSC prelims examinations for thorough preparation.

Electrolysis calculationsElectrode potentialNernst equationDrift velocityFuel cellsMolar conductivity

Electrochemistry and Current Electricity Questions

Multiple choice physics electric current, potential difference and resistance drift velocity and mobility drift speed drift velocity & mobility

The number of free electrons per $10$ mm ordinary copper wire is about $2\times 10^{21}$. The average drift speed of the electrons is $0.25$ mm current flowing is:

  1. $0.8$ A
  2. $8$ A
  3. $80$ A
  4. $5$ A
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given,

Number of electron, $n=2\times {{10}^{21}}$

Average drift speed, $0.25\,mm/s$

$ Q=ne $

$ Q=2\times {{10}^{21}}\times 1.6\times {{10}^{-19}} $

$ Q=320\,C $

Since,

$ s=\dfrac{D}{T} $

$ T=\dfrac{D}{s} $

$ T=\dfrac{10}{0.25}=40 $

So, current

$ I=\dfrac{Q}{T} $

$ I=\dfrac{320}{40} $

$ I=8\,A $

Multiple choice physics electric current drift velocity and mobility drift speed drift velocity & mobility

The drift of the electrons in a copper-wire of length 2 m under the application of potential difference of $ 200 V is 0.5 ms^{-1} $ . their mobility is $ (inm^2V^{-1}s^{-1} ) $

  1. $ 2.5 \times 10^{-3} $
  2. $ 2.5 \times 10^{-2} $
  3. $ 5 \times 10^{2} $
  4. $ 5 \times 10^{-3} $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Mobility mu = v_d / E. E = V / L = 200 / 2 = 100 V/m. mu = 0.5 / 100 = 0.005 = 5 x 10^-3 m^2/Vs.

Multiple choice physics electric current, potential difference and resistance drift velocity and mobility drift speed drift velocity & mobility

Copper contains $8.4\times 10^{28}$ free electrons$/m^3$. A copper wire of cross-sectional area $7.4\times 10^{-7}m^2$ carries a current of $1$A. The electron drift speed is approximately.

  1. $10^{-8}$m/s
  2. $10^3$m/s
  3. $1$m/s
  4. $10^{-3}$m/s
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$v=\dfrac{I}{ne}=\dfrac{1}{7.4\times 10^{-7}}\times 8.4\times 10^{28}$
$=\dfrac{10^{-2}}{8.4\times 1.6\times 7.4}=10^-3$.

Multiple choice physics electric current, potential difference and resistance drift velocity and mobility drift speed drift velocity & mobility

a current 10 ampere is maintained in a conductor of cross section of $ 10^{-4}m^2 $. if the electron density is $ 9 \times 10^{28} m^{-3} $ , what is the drift velocity of free electrons?

  1. $ 6.9 \times 10^{-6} ms^{-1} $
  2. $ 6.9 \times 10^{-4} ms^{-1} $
  3. $ 6.9 \times 10^{5} ms^{-1} $

  4. none of thses
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

v_d = I / (neA). I = 10, n = 9e28, A = 1e-4, e = 1.6e-19. v_d = 10 / (9e28 * 1.6e-19 * 1e-4) = 10 / (14.4e5) = 10 / 1440000 = 6.94e-6 m/s.

Multiple choice chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

How many minutes will it take to plate out $5.0g$ of $Cr$ form a $Cr _2(SO _4) _3$ solution using a current of $1.50A$?

  1. $254$
  2. $309$
  3. $152$
  4. $103$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using Faraday's law, mass = (I * t * M) / (n * F). For Cr2(SO4)3, Cr is in the +3 oxidation state (n=3). Molar mass of Cr is 52g/mol. t = (5.0 * 3 * 96500) / (1.5 * 52) = 18557 seconds. 18557 / 60 = 309 minutes.

Multiple choice physics electrical quantities electric potential and potential difference potential difference current in electric circuits

how many electrons should pass through a conductor in $1$ second to constitute 1 amp current, it the charge one Eatonton is $1.6\times{10}^{-19}$

  1. $6.25\times{10}^{18}$
  2. $6.9\times{10}^{18}$
  3. $6.5\times{10}^{19}$
  4. $6.25\times{10}^{15}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

1 ampere means 1 coulomb of charge flows per second. Since each electron carries 1.6 × 10^-19 C, the number of electrons needed is 1 ÷ (1.6 × 10^-19) = 6.25 × 10^18. Option A correctly shows this calculation.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

An aluminium (Al) rod with area of cross-section $4\times 10^{-6}m^2$ has a current of 5A. Flowing through it. Find the drift velocity of electron in the rod. Density of $Al=2.7\times 10^3kgm^{-3}$ and atomic wt.=27. Assume that each Al atom provides one electron.

  1. $8.6\times 10^{-4}ms^{-1}$
  2. $6.2\times 10^{-4}ms^{-1}$
  3. $1.2\times 10^{-4}ms^{-1}$
  4. $3.8\times 10^{-3}ms^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Drift velocity v_d = I / (n*A*e). The number density n = (density * Avogadro's number) / atomic weight. Calculating n for Aluminum and substituting into the formula yields approximately 1.2*10^-4 m/s.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

The number of free electrons passing through the filament of an electric lamp is one hour when the current through the filament is 0.32 A will be 

  1. $3\times { 10 }^{ 22 }$
  2. $2\times { 10 }^{ 26 }$
  3. $7.2\times { 10 }^{ 19 }$
  4. $7.2\times { 10 }^{ 21 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Total charge Q = I * t = 0.32 A * 3600 s = 1152 C. Number of electrons n = Q / e = 1152 / 1.6*10^-19 = 7.2*10^21.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

The number of electrons striking the screen of CR is $7.5\times 10^{15}$ in 10 s. Calculate the electric current

  1. $1.2\times10^{-4}$
  2. $7.5\times10^{-4}$
  3. $1.6\times10^{-4}$
  4. $1.2\times10^{-5}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Current I = q / t = (n * e) / t = (7.5*10^15 * 1.6*10^-19) / 10 = 1.2*10^-4 A.

Multiple choice physics electric current, potential difference and resistance electric potential and potential difference potential difference current in electric circuits

In electrolysis, mass of the substance liberated at cathode is proportional to 

  1. strength of the current passed.

  2. time of passage of current.

  3. quantity of electricity passed.

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to the first law of electrolysis the mass of of substance liberated at cathode is proportional to the quantity of electric charge passed through it or indirectly it's proportional to the quantity of  electricity  passed. 

$\because$ $m= k \times q$

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

$H^{+}$ ions are reduced at platinum electrode prior to__________.

  1. $Zn^{2+}$
  2. $Cu^{2+}$
  3. $Ag^{+}$
  4. $I _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$H^+$ ions are reduced at platinum electrode prior to $Zn^{2+}$.

Because reduction potential of $\underset {(aq.)}{Zn^{+2}}+2e^- \longrightarrow Zn (s)$  $(-0.76)$
It means that it favours for oxidation rather than reduction.
Where reduction potential of $\underset {(aq.)}{2H^+}+2e^- \longrightarrow H _2 (g)$         $ (0)$
                                                  $\underset {(aq.)}{Cu^{+2}}+2e^- \longrightarrow Cu (s)$     $(0.16)$
                                                  $\underset {(aq.)}{Ag^+}+e^- \longrightarrow Ag(s)$         $(0.22)$
                                                  $\underset {(s)}{I _2}+2e^- \longrightarrow \underset {(aq.)}{2I^-} $               $(0.54)$

Multiple choice physics static electricity explaining static electricity charging by induction electric charges and fields

The number of electrons that must be removed from an electrically neutral silver dollar to give it a charge of $+2.4C$ is

  1. $2.5\times { 10 }^{ 19 }$
  2. $1.5\times { 10 }^{ 19 }$
  3. $1.5\times { 10 }^{ -19 }$
  4. $2.5\times { 10 }^{ -19 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Total charge, $q=+2.4C$
Then by quantization of charge $q=ne$
$\therefore$ number of electrons, $\quad n=\cfrac { q }{ e } =\cfrac { 2.4C }{ 1.6\times { 10 }^{ -19 } } =1.5\times { 10 }^{ 19 }\quad \quad $

Multiple choice biology absorption by roots - the processes involved manure manures and fertilisers water absorption organ

A root hair cell under ordinary conditions have a water potential in the range of?

  1. $-1$ to $-4$ atm.
  2. $-1$ to $+4$ atm.
  3. $1$ to $2$ atm.
  4. $-1$ to $2$ atm.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Under ordinary conditions, the water potential of a root hair cell is negative, typically ranging between -1 and -4 atm, which allows it to absorb water from the soil.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

When an electric current is passed through an aqueous solution of the following, the concentrations of cation as well as anion will not change for (assume constant volume of the electrolytic solution)

  1. $ C _{S} CI $
  2. $ KNO _{3}$
  3. $ AgNO _{3}$
  4. $ HCI$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

KNO3 is a strong electrolyte where both K+ and NO3- ions have high reduction/oxidation potentials compared to water. During electrolysis, water is preferentially electrolyzed, leaving the concentration of K+ and NO3- ions effectively unchanged.