Video Lecture
Theory For Notes Making
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Objective Assignment
1.
The resistance of an ammeter of 1–ampere range is 1 ohm. Calculate the resistance of the shunt, which will increase the range of the ammeter to 10 amperes.
(a) \frac{1}{5}\,\,\Omega
(b) \frac{1}{9}\,\,\Omega
(c) \frac{1}{3}\,\,\Omega
(d) \frac{1}{15}\,\,\Omega
Ans (b)
2.
A voltmeter has got a resistance of . What alteration in it will have to be made so as to increase its range twenty times?
(a) 90000\,\,\Omega
(b) 85000\,\,\Omega
(c) 5000\,\,\Omega
(d) 95000\,\,\Omega
Ans (d)
3.
A cyclotron’s oscillator frequency is 1 MHz. What should be the operating magnetic field for accelerating protons? If the radius of the Dees is 60 cm, what is the kinetic energy of the proton beam? {{m}_{p}}=1.67\times {{10}^{{-27}}}\,\,kg. Express your result in MeV (1 MeV=1.6\times {{10}^{{-13}}}\,\,J)
(a)0.60T, 7.2 MeV
(b)0.50T, 6.5 MeV
(c)0.66T, 7.4 MeV
(d)0.80T, 8.0 MeV
Ans (c)
Subjective Assignment
Q.1.
Define the current sensitivity of a moving coil galvanometer.And give any two factors to improve it ?
Q.2.
State principle of moving coil galvanometer.
Q.3.
State two factors on which the sensitivity of a moving coil galvanometer depends.
Q.4.
What is the nature of the magnetic field in a moving coil galvanometer ?
Q.5.
Why a radial magnetic field is used in a galvanometer?
Q.6.
Why soft iron core is used for the coil in a galvanometer.
Q.7.
Explain the theory of cyclotron. Why is cyclotron not suitable for accelerating electrons ‘?
Q.8.
A cyclotron is used to accelerated alpha particle and eject the stream of alpha particles with velocity `v1’. If the same cyclotron is used to accelerate protons they come out with a velocity `v2’. What is the ratio of v1&v2.
Q.9.
Describe the principle and construction of a moving coil galvanometer. Prove that the current flowing in the coil is directly proportional to its deflection. What is the importance of the radial field’?
Q.10.
What are drawbacks of a simple cyclotron and their remedies ?
Q.11
In side a galvanometer a horse shoe magnet with circular poles produces a radial magnetic field of 0.5T, the torsional constant of the springs is 100Nm/rad.If the coil has a dimension of 6x4cm with 1000turns then find the current sensitivity of the galvanometer.Use \displaystyle \mu rof core of the coil as 600.
Q.12
A galvanometer has a magnetic field of 5000G and a coil of 4x3cm with air core and 500 turns is used.If the torsional constant is100Nm/rad then graduate the scale of this galvanometer.
Q.13
Compare the voltage sensitivity of two galvanometer having their magnetic field in the ratio 2:1, their resistance in the ratio 3:2,number of turns in the ratio 1:4 with same dimensions of the coil in them and same type of spring.
Q.14
A galvanometer having 30 division has a current sensitivity of 20 \displaystyle \mu A/division.It has a resistance of 25 \displaystyle \Omega . How will you convert it into an ammeter measuring upto 1Amp. How will you convert this galvanometer into a voltmeter of range 0-1volt ?
Q.15
The moving coil of a galvanometer 4 cm along and 1.5 cm wide, made of 200 turns of thin wire, works in a magnetic field with induction of 0.1 T. The plane of the coil is parallel to lines of induction. Find the torque acting on the coil when the is current of 1 mA flows in it.
Q.16
The moving coil of a galvanometer made of 200 turns of thin wire is suspended from an elastic thread. The area of the coil is 1 cm2, it coincides in direction with the lines of induction of a magnetic field with induction of 15 mT.When the current of 5.0 \displaystyle \mu A is passed through the coil turn with a current of 7.5 \displaystyle \mu a? What is the torsion modulus of the thread?
Q.17
A moving coil galvanometer has the following configuration:
N = 24 , area of the coil = 0.002m2, B = 0.2T
R = 14 \displaystyle \Omega
(a) Indicate a simple way to increase the current sensitivity of the meter by 25% without changing area or magnetic field.
(b)If in doing so the resistance of the meter increases to 21 \displaystyle \Omega is the voltage sensitivity of the meter greater or less than the original meter?
Q.18.
A moving coil galvanometer consists of a rectangular coil of N turns, each of area A, suspended in a radial magnetic field of flux density \displaystyle \Omega
A. Derive the expression for the torque on the coil, when current I passes through it. Draw suitable labelled diagram.