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What are the important topics covered in Class 12 Physics Chapter 3 solutions?
What are the important topics covered in Class 12 Physics Chapter 3 solutions?
The topics focused on while preparing the Current Electricity NCERT solutions are:
Ohm's law
Drift velocity
Resistivity vs temperature
Combination of cells
Kirchhoff's rules and
Wheatstone bridge
Upvote 
A galaxy is moving away from the earth at a speed 286 kms-1. The shift in wavelength of a redline at 630 nm is x×10-10 m. The value of x, to the nearest integer, is.
[Take the value of speed of light c, as 3×108 ms-1]
A galaxy is moving away from the earth at a speed 286 kms-1. The shift in wavelength of a redline at 630 nm is x×10-10 m. The value of x, to the nearest integer, is.
[Take the value of speed of light c, as 3×108 ms-1]
Δλ = (v/c)λ = (286/3000000) × 630 × 10? = 6.006 × 10? ¹? ≈ 6 × 10? ¹? m
Upvote A small toy starts moving from the position of rest under a constant acceleration. If it travels a distance of 10m in t s, the distance travelled by the toy in the next t s will be:
A small toy starts moving from the position of rest under a constant acceleration. If it travels a distance of 10m in t s, the distance travelled by the toy in the next t s will be:
According to question, we can write
10 =
Upvote In a meter bridge, the point D is a neutral point (figure).
(a) The meter bridge can have no other neutral. A point for this set of resistances.
(b) When the jockey contacts a point on meter wire left of D, current flows to B from the wire
(c) When the jockey contacts a point on the meter wire to the right of D, current flows from B to the wire through galvanometer
(d) When R is increased, the neutral point shifts to left
In a meter bridge, the point D is a neutral point (figure).
(a) The meter bridge can have no other neutral. A point for this set of resistances.
(b) When the jockey contacts a point on meter wire left of D, current flows to B from the wire
(c) When the jockey contacts a point on the meter wire to the right of D, current flows from B to the wire through galvanometer
(d) When R is increased, the neutral point shifts to left
This is a Multiple Choice Questions as classified in NCERT Exemplar
Answer – (a, c)
Explanation- In case of meter bridge, the resistance wire AC is 100 cm long. Varying the position of tapping point B, bridge is balanced. If in balanced position of bridge AB = l, BC = (100 – l) so that Q/P= (100-l)/l.
Upvote The measurement of an unknown resistance R is to be carried out using Wheatstone bridge as given in the figure. Two students perform an experiment in two ways. The first student takes R2= 10 Ω and R1 = 5 Ω. The other student takes R2 = 1000 Ω, and R1 = 500 Ω. In the standard arm, both take R3 = 5 Ω.
Both find R = R2/R1, R3 = 100 Ω within errors.
(a) The errors of measurement of the two students are the same
(b) Errors of measurement do depend on the accuracy with which R2 and R1 can be measured
(c) If the student uses large values of R2 and R1, the currents through the arms will be feeble. This will make determination of null point accurately more difficult.
(d) Wheatstone bridge is a very accurate instrument and has no errors of measurementAnswer – (b,c)
The measurement of an unknown resistance R is to be carried out using Wheatstone bridge as given in the figure. Two students perform an experiment in two ways. The first student takes R2= 10 Ω and R1 = 5 Ω. The other student takes R2 = 1000 Ω, and R1 = 500 Ω. In the standard arm, both take R3 = 5 Ω.
Both find R = R2/R1, R3 = 100 Ω within errors.
(a) The errors of measurement of the two students are the same
(b) Errors of measurement do depend on the accuracy with which R2 and R1 can be measured
(c) If the student uses large values of R2 and R1, the currents through the arms will be feeble. This will make determination of null point accurately more difficult.
(d) Wheatstone bridge is a very accurate instrument and has no errors of measurementAnswer – (b,c)
Answer – (b, c)
Explanation – According to the relation that p/q=r/s if galvanometer shows no deflection. In the above equation the value of R4 depends upon R1 and R2 . if the value of R1 and R2 will be feeble the value of R4 would be affected.
Upvote Temperature dependence of resistivity ρ(T) of semiconductors, insulators and metals is significantly based on the following factors:
(a) Number of charge carriers can change with temperature T.
(b) Time interval between two successive collisions can depend on T.
(c) Length of material can be a function of T.
(d) Mass of carriers is a function of T.
Temperature dependence of resistivity ρ(T) of semiconductors, insulators and metals is significantly based on the following factors:
(a) Number of charge carriers can change with temperature T.
(b) Time interval between two successive collisions can depend on T.
(c) Length of material can be a function of T.
(d) Mass of carriers is a function of T.
This is a Multiple Choice Questions as classified in NCERT Exemplar
Explanation- according to the relation = also T
Upvote Consider a simple circuit shown in figure stands for a variable resistance R’. R’ can vary from R0to infinity, r is internal resistance of the battery (r <<r<<r’).
</r<<r’).
(a) Potential drop across AB is nearly constant as R’ is varied.
(b) Current through R’ is nearly a constant as R’ is varied.
(c) Current I depends sensitively on R’
(d) I ≥ V/r + R always;
Consider a simple circuit shown in figure stands for a variable resistance R’. R’ can vary from R0to infinity, r is internal resistance of the battery (r <<r<<r’).
</r<<r’).
(a) Potential drop across AB is nearly constant as R’ is varied.
(b) Current through R’ is nearly a constant as R’ is varied.
(c) Current I depends sensitively on R’
(d) I ≥ V/r + R always;
This is a Multiple Choice Questions as classified in NCERT Exemplar
Answer – (a, d)
Explanation- potential drop across AB is independent to R' also when we decrease the value of R the current will also very large. According to the relation I=e/R+r
Upvote Kirchhoff’s junction rule is a reflection of
(a) Conservation of current density vector.
(b) Conservation of charge.
(c) The fact that the momentum with which a charged particle approaches a junction is unchanged (as a vector) as the charged particle leaves the junction.
(d) The fact that there is no accumulation of charges at a junction.
Kirchhoff’s junction rule is a reflection of
(a) Conservation of current density vector.
(b) Conservation of charge.
(c) The fact that the momentum with which a charged particle approaches a junction is unchanged (as a vector) as the charged particle leaves the junction.
(d) The fact that there is no accumulation of charges at a junction.
This is a Multiple Choice Questions as classified in NCERT Exemplar
Answer – (b, d)
Explanation-Algebraic sum of the currents flowing towards any point in an electric network is zero. It also tell us about the conservation of charge.
Upvote Which of the following characteristics of electrons determines the current in a conductor?
(a) Drift velocity alone
(b) Thermal velocity alone
(c) Both drift velocity and thermal velocity
(d) Neither drift nor thermal velocity
Which of the following characteristics of electrons determines the current in a conductor?
(a) Drift velocity alone
(b) Thermal velocity alone
(c) Both drift velocity and thermal velocity
(d) Neither drift nor thermal velocity
This is a Multiple Choice Questions as classified in NCERT Exemplar
Answer- (a)
Explanation- I=AneVd , current is directly proportional to drift velocity.
Upvote A metal rod of length 10 cm and a rectangular cross-section of 1 cm x 1/2 cm is connected to a battery across opposite faces. The resistance will be
(a) Maximum when the battery is connected across 1 cm x 1/2 cm faces
(b) Maximum when the battery is connected across 10 cm x 1 cm faces
(c) Maximum when the battery is connected across 10 cm x 1/2 cm faces
(d) Same irrespective of the three faces
A metal rod of length 10 cm and a rectangular cross-section of 1 cm x 1/2 cm is connected to a battery across opposite faces. The resistance will be
(a) Maximum when the battery is connected across 1 cm x 1/2 cm faces
(b) Maximum when the battery is connected across 10 cm x 1 cm faces
(c) Maximum when the battery is connected across 10 cm x 1/2 cm faces
(d) Same irrespective of the three faces
This is a Multiple Choice Questions as classified in NCERT Exemplar
Answer- (a)
Explanation- R= for greater value of R, A should be less and its possible value when connected across 1cm 1/2cm faces.
Upvote