Tag: current in electric circuits

Questions Related to current in electric circuits

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

If the strenath of the majestic field produced $10 \mathrm { cm }$ away from a infinitely long straight conductor is $10 ^ { - 5 } \text { weber/m } ^ { 2 }$ the value of the current flowing in the conductor will be:

  1. $5\ ampere$

  2. $10\ ampere$

  3. $500\ ampere$

  4. $1000\ ampere$

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The magnetic field B of an infinite wire is B = (mu_0 * I) / (2 * pi * r). Rearranging for I: I = (B * 2 * pi * r) / mu_0. Given B = 10^-5, r = 0.1m, and mu_0 = 4*pi*10^-7, I = (10^-5 * 2 * pi * 0.1) / (4 * pi * 10^-7) = 5 A.

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

If current density in a conducting wire is proportional to the distance r from the axis of the conductor, then find magnetic field at the position r<R , where R is the radius of cross section of the conductor.('i'is the current in conducting wire)

  1. $ \frac { \mu _0ir^2 }{2 \pi R^3} $

  2. $ \frac { \mu _0ir^2 }{4 \pi R^3} $

  3. $ \frac { \mu _0ir^2 }{2 \pi R^2} $

  4. $ \frac { \mu _0ir^2 }{2 \pi R^4} $

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Using Ampere's Law, integral(B dl) = mu_0 * I_enclosed. If current density J = kr, then I_enclosed = integral(J * 2*pi*r dr) from 0 to r. Solving this and relating k to total current I gives the field B = (mu_0 * I * r^2) / (2 * pi * R^3).

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

Electric current flows from positive terminal of battery to negative terminal.

  1. True

  2. False

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

By convention, the direction of conventional electric current is defined as the flow of positive charge, which is from the positive terminal to the negative terminal.

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

Two conducting parallel plates areseparated by a distance of 0.001$\mathrm { m } . \mathrm { A } 9 \mathrm { V }$battery is connected across the plates.Find out the electric field between the plates? 

  1. 9000$\mathrm { V } / \mathrm { m }$

  2. 900$\mathrm { Vim }$

  3. 9$\mathrm { V } / \mathrm { m }$

  4. <span>.9$\mathrm { V } / \mathrm { m }$</span>

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The electric field E between parallel plates is given by E = V / d. Given V = 9 V and d = 0.001 m, E = 9 / 0.001 = 9000 V/m.

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 current density $ \bar { j }  $ at cross-sectional area $ \bar { A } = (2 \hat {i} + 4 \hat {j} )mm^{-2}$  is $(2 \hat {j} + 2 \hat {k} ) A m^{-2} $ The current following through the cross-sectional area is

  1. $ 12 \mu A $

  2. $ 8 \mu A $

  3. $ 4 \mu A $

  4. zero

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

Current I = J dot A. Given J = (2j + 2k) A/m^2 and A = (2i + 4j) mm^2 = (2i + 4j) * 10^-6 m^2. The dot product is (0*2 + 2*4 + 2*0) * 10^-6 = 8 * 10^-6 A = 8 microA.

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

A flow of $10^{12}$ electrons per minute in a conducting wire constitutes a current of 

  1. $1.6 \times 10^{-7}\, A$

  2. $1.6 \times 10^{-8}\, A$

  3. $2.67 \times 10^{-9}\, A$

  4. `$2.67 \times 10^{-10}\, A$

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Current I = q / t. Total charge q = 10^12 * 1.6*10^-19 = 1.6*10^-7 C. Time t = 60 s. I = 1.6*10^-7 / 60 = 2.67*10^-9 A.

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 a conductor, $6.25\, \times\, 10^{16}$ electrons flow from its end A to B in 2 s. Which is the current flowing through conductor? $(e\, =\, 1.6\, \times\, 10^{-19}\, C)$  

  1. $5 mA$ from B to A.

  2. $5 mA$ from A to B.

  3. $10 mA$ from A to B.

  4. $10 mA$ from B to A.

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the question, it is given that the charge of an electron is $e=1.6\times { 10 }^{ -19 }\quad C$.

Therefore, the total charge flowing through the wire in 2 seconds will be given as $6.25\times { 10 }^{ 16 }\times 1.6\times { 10 }^{ -19 }\quad C\quad =10\times { 10 }^{ -3 }\quad C$.

The rate of flow of charge is therefore $\dfrac { 10\times { 10 }^{ -3 } \  C }{ 2  \ seconds\quad  } =5\times { 10 }^{ -3 }\quad C/s$.

one C/s = one amp.

Hence, the current flowing through a conductor is $0.0005 A$, that is $5 mA$.