The figure below shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 Ω maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.04 V (for very moderate currents up to a few mA) gives a balance point at 67.3 cm length of the wire. To ensure very low currents drawn from the standard cell, a very high resistance of 600 KΩ is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf Ꜫ and the balance point, found similarly, turns out to be at 82.3 cm length of the wire. What is the value Ꜫ?
(a) 0.25 V
(b) 2.25 V
(c) 3.25 V
(d) 1.25 V
(a) 0.25 V
(b) 2.25 V
(c) 3.25 V
(d) 1.25 V
(d) 1.25 V
The figure below shows a 2.0 V potentiometer used for the determination of internal resistance of a 1.5 V cell. The balance point of the cell in open circuit is 76.3 cm. When a resistor of 9.5 Ω is used in the external circuit of the cell, the balance point shifts to 64.8 cm length of the potentiometer wire. Determine the internal resistance of the cell.
(a) 1.7 Ω
(b) 2.7 Ω
(c) 3.7 Ω
(d) 1.1 Ω
A cell of emf E and internal resistance r is connected to two external resistances R₁ and R₂ and a perfect ammeter. The current in the circuit is measured in four different situations :
(i) without any external resistance in the circuit
(ii) with resistance R1 only
(iii) with R1 and R2 in series combination
(iv) with R1 and R2 in parallel combination.
The currents measured in the four cases are 0.42 A, 1.05 A, 1.4 A and 4.2 A, but not necessarily in that order. Identify the currents corresponding to the four cases mentioned above.
A student connects a cell, of emf E2 and internal resistance r2 with a cell of emf E1 and internal resistance r1, such that their combination has a net internal resistance less than r1. This combination is then connected across a resistance R. Draw a diagram of the 'set-up' and obtain an expression for the current flowing through the resistance.
A battery of emf 12 V and internal resistance 2 Ω is connected to a 4 Ω resistor as shown in the figure.
(i) The potential difference applied across a given resistor is altered so that the heat produced per second increases by a factor of 9. By what factor does the applied potential difference change ?
(ii) In the figure shown, an ammeter A and a resistor of 4 W are connected to the terminals of the source. The emf of the source is 12 V having an internal resistance of 2 W. Calculate the voltmeter and ammeter readings.
(i) Why do the 'free electrons', in a metal wire, 'flowing by themselves', not cause any current flow in the wire ?
Define 'drift velocity' and obtain an expression for the current flowing in a wire, in terms of the 'drift velocity' of the free electrons.
(ii) Use the above expression to show that the 'resistivity', of the material of a wire, is inversely proportional to the 'relaxation time' for the 'free electrons' in the metal.
A cell of emf ‘E’ and internal resistance ‘r’ is connected across a variable load resistor R. Draw the plots of the terminal voltage V versus (i) R and
(ii) the current I.
It is found that when R = 4 Ω, the current is 1 A when R is increased to 9 Ω, the current reduces to 0.5 A. Find the values of the emf E and internal resistance r.
Unpolarized light is incident on a plane glass surface The angle of incidence so that reflected and refracted rays are perpendicular to each other, them
(a) tan iβ= μ/2
(b) tan iβ = μ
(c) sin iβ = μ
(d) cos iβ = μ
What is the shape of the magnet in Moving Coil Galvanometer to make the torque maximum?
a) Horse Shoe
b) Convex
c) Concave
d) None of these.
The light sources used in Young’s double slit experiment are:
(A) Incoherent
(B) Coherent
(C) White light
(D) Blue-green-red Light.
In the above diagram \(C_2\) is twice of Capacitance of \(C_1\) which is C. Find the ratio of energy stored in the combination before and after the insertion of of a dielectric constant K in both the capacitors.(Battery is disconnected)
In Young’s double slit experiment, the fringe width is β . If the entire arrangement is now placed inside a liquid of refractive index μ , the fringe width will become
(a) μ β
(b) β/μ
(c) β/μ+1
(d) β/μ−1
The locus of all particles in a medium, vibrating in the same phase is called
(a) wavelet
(b) fringe
(c) wave front
(d) None of these
Two sources of intensity I and 4I are used in an interference experiment . Find the intensity at points where waves from two sources superimpose with phase difference π/2 is
I. 4I
II. 6I
III. 5I
IV. 9I