# Class 10 Physics Electromagnetism 15.12. What is a transformer? Explain the working of a transformer in connection with mutual induction.

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##### 15.12. What is a transformer? Explain the working of a transformer in connection with mutual induction.

A current carrying conductor is placed in a uniform magnetic field parallel to it. The magnetic force experienced by the conductor is:A) F=I / B B) F=I / B \sin \theta C) \mathrm{F}=0 D) \mathrm{F}=\mathrm{l} / \mathrm{B} \cos \theta

15.8. What are the factors which affect the magnitude of the e.m.f. induced in a circuit by a changing magnetic field?

Magnetic lines of force.A) Intersect at infinityB) Cannot intersect at allC) Intersect with in the magnetD) Intersect at the neutral points

14.12. An Iron core solenold with 400 turns has a cross section area of 4.0 \mathrm{~cm}^{2} . A current of 2 amp passing through it produces \mathrm{B}=0.5 webers-m { }^{-2} . How targe an emf is induced in it. If the current is twrned of in 0.1 seconds. What is the self Inductance of the solenold ? (Ans 0.8 \mathrm{~V} L=40 \mathrm{mh} ).

15.1. Suppose someone handed you three similar iron bars and told you one was not magnet but the other two were. How would you find the iron bar that was notmagnet?

The relationship between tesla (T) and smaller unit Gauss ( G ) of magnetic induction is given by:A) 1 \mathrm{~T}=10^{3} \mathrm{G} B) 1 \mathrm{~T}=10^{-4} \mathrm{G} C) 1 \mathrm{~T}=10^{-2} \mathrm{G} D) 1 \mathrm{~T}=10^{4} \mathrm{G}

What shunt resistance must be connected across a galvanometer of 50.0 \Omega resistance which gives full scale deflection with 2.0 \mathrm{~mA} current so as to convert it into an ammeter of range 10.0 \mathrm{~A} ?

The magnetic field in a certain region is given by \vec{B}=(40 \hat{i}-18 \hat{k}) wb \mathrm{m}^{-2} . How much flux passes through a 5.0 \mathrm{~cm}^{2} area loop in this region if the loop lies flat in the x y - plane?

14.4 A coil of 0.1 \mathrm{~m} \times 0.1 \mathrm{~m} and of 200 turns carrying a current of 1.0 \mathrm{~mA} is placed in a uniform magnetic field of 0.1 \mathrm{~T} . Calculate the maximum torque that acts on the coil.(Ans: 2.0 \times 10^{-4} \mathrm{Nm} )

15.4. When a straight current-carrying conductor is placed in a magnetic field it experiences a force. State the rule by which the direction of this force can be found out.

15.5. A conductor wire generates a voltage while moving through a magnetic field. In what direction should the wire be moved relative to the field to generate the maximum voltage?

15.9. Can a transformer operate on direct current?

(i) Like poles of a magnet each other.(a) attract (b) repel (c) neither attract nor repel (d) somctimes

The direction of force due to earths magnetic field on a wire carrying current vertically downward isA) Horizontally towards eastB) Horizontally towards northC) Horizontally towards westD) None of these

14.8. Derlve the general equation for Induced emf begining with the law of force in a current carrying conducto: in a magnetic fleld.

The SI unit of magnetic induction is tesla which is also equal to:A) Newton / ampere-meter or N/A-mB) Newton / ampere-meter { }^{2} or N/A-m { }^{2} C) Newton / ampere { }^{2} -meter or N / A^{2}-m D) None of these

14.2. Charged particles fred in vacisum tube hit a fuorescent screen. Will it be possible to know whether they are positive or negative?

An ideal transformer is used to step up an alternating emf of 220 \mathrm{~V} to 4.4 \mathrm{KV} to transmit 6.6 \mathrm{KW} of power. The current rating of the secondary is.A) 30 \mathrm{~A} B) 3 \mathrm{~A} C) 1.5 \mathrm{~A} D) 1 \mathrm{~A}

The SI unit of magnetic flux is:A) \mathrm{NmA}^{-1} B) \mathrm{NAm}^{-1} C) \mathrm{NmA}^{-2} D) \mathrm{Nm}^{2} \mathrm{~A}^{-1}

15.2. A step-up transformer has a turn ratios of 1: 100 . An alternating supply of 20 \mathrm{~V} is connected across the primary coil. What is the secondary voltage? Ans. (2000 V)

A solenoid 15.0 \mathrm{~cm} long has 300 turns of wire. A current of 5.0 A flows through it. What is the magnitude of magnetic field inside the solenoid?

The standard vector symbol for flux density is:A) \varepsilon_{r} B) \varepsilon_{0} C)D)B

(ii)Explain the right hand rule for the magnetic force.

A moving charged is subjected to an external magnetic field. The change in the kinetic energy of the particleA) Increases with the increase in the field strength.B) Decreases with the increase in the field strength.C) Is always zero.D) Depends upon whether the field is uniform or non-uniform.

15.1. Demonstrate by an experiment that a magnetic field is produced around a straight current-carrying conductor.

14.12 What should be the orientation of a current carrying coil in a magnetic field so that torque acting upon the coil is (a) maximum (b) minimum?

14.11. An cm of 45 \mathrm{~m} .volt is Induced In a coll of 500 turns. when the current in a nelghbouring coil changes from 10 amps to 4 amps in 0.2 seconds.b) What is the rate of change of fux in the second coll?

Example 14.1.A proton enters a unlform magnetic fleld of Ir:duction \mathrm{B}=0.300 Tesla In a direction making an angle of 45^{\circ} with the directlon of neld. What will be the magnttude of force if the velocity of proton is 10^{4} \mathrm{n} is?