14.magnetic effect of electric current (physics - chapter wise question bank)

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Chapter 14: Magnetic Effect ofElectric Current

81 . Question Obj/ Spec.!

No. Ditr. Level

1. Magnetic tield due to a current carrying element of length d I at a K

point distant r from it is directly proportional to Recall

a) strength of the current I Easy

b) length of the current element dlc) 1 J [2

d) all these

Ans : d)

2. Two conductors of equal lengths carrying equal amount of current Sheld perpendicular to each other. Mark the direction of the Draws,

magnetic field due to this combination in the four regions by dots locate

and crosses: Difficult

227



Correct markin g : 2 marks

3. A current carrying conductor is passed through a cardboard on U

which iron filings are spread horizontally. Mark the magnetic lines Draw

offorce with direction. Average

tj:

r II II

Correct marking (1 mark)

4. A coil consisting of 50 turns creates a field of 3.5 x 10.5 T. A

Compute the value of current flowing in the coil (Given radius of Solvethe coil = 0.08 m) Average

B= ~ ( 21l n I)41 l r

i.e. I= 2 Br (1 mark)f . . ln n

I = 2 x 3.5 x 10-5

x 0.08 = 0.089 A (1 mark)41l x 10-1x 50

uruc

228



I I P U C

5. The lines passing through places of equal declination are called

f a) agonic lines

b) isoclinals

c) isogonals

d) isodynamic lines

K

Recall

Easy

Ans: c)

6. Lines passing through places

component are called as

a) isogonals

b) isodynamic lines

c) agonic lines

d) isoclinals

of the same value of horizontal K

Recall

Easy

Ans: b)

7. A circular current carrying conductor produces a magnetic field. U

Derive an expression for the magnetic field at a point on the axial Interpret,

line. Explain,

Derive

Average

Diagram with specifications (lmark)

P ( I d l s i n B )pply Laplace Law dB =_0 2

4ff r(1 mark)

Show that the cosine components cancel (Imark)

Arrive at

_ Po [ 2 ff n I r2 ]B - - 2 2 3/2 (2 marks)

4 ff (r +x)

8 . State, explain and give the mathematical form Biot-Savart's law.

Explain the terms with a diagram. Give the vector form of the law.

K

State, Recall,

Label

Explanation of the concept with diagram (1mark).

Statement of law (2 marks)

Mathematical representation (I mark)

dB ~ ( :~ ) ( l d : : i n B )Vector representation of the law i.e.

dB ~ ( ::) I~, x r (Imark)

229



I I PUC

9. State Laplace's law for a current carrying element which produces a K

magnetic field. State,Recall

Easy

Statement only (2 marks)

10. Write Laplace's law is mathematical form when a current carrying K

element produces a magnetic field. Give its vector fonn. Recall

Easy

dB ~ (:~) ( 1 d ~:in 0 ) (1mark)

- ( 1 1 ) I d I x;:Vector form, dB = 4~ rJ (1mark)

11. Write an expression for the magnetic field produced by a current U

carrying circular coil at its centre. Show graphically the variation Recall and

of field with distance on the axial line. Draw

Average

Expression (1 mark)

Graph (lmark)

12. Write an expression for the magnetic moment of a current loop and K

explain the symbols used. RecallEasy

M=nlA (I mark)

M - magnetic moment

I-current in a loop

A - Area of the current loop (I mark)

13. At one end of an ideal current carrying long solenoid, the magnetic U

field is See

a) B=Ilonl relationship

II I Average

b) B = ! : : ! ! . . . ! ! _2

c) B=41lonI

d) B=2 IlonT

Ans: b)

230



II PUC

14. Show graphically the variation of magnetic field along the axis of S

"an ideal solenoid. Draw graph,

Mark the length of the solenoid in the graph. interpret

Difficult

;1

(lmark)

I~~- --::;

Lel\.l~TH

Field is uniform over major part of the solenoid of length L.(1 mark)

15. Write an expression for the magnetic field at a point on the axis of a K

solenoid. Explain the symbols with the help of a diagram. Recall

Easy

B = Po nl (cos $1 - cos $2 ) (1 mark)2

Explanation of the terms with diagram (1 mark)

16. Magnetic field due to a current carrying ideal solenoid at its mid U

point on its axis is See

a) B = Po nl relationship

2 Average

b) 2!1onI

c) B =4 J . l o nl

d) B =J-lonl

Ans: d)

17. Give the theory of tangent galvanometer. U

Explain

Average

Explaining that the coil must be placed such that its field at its

centre is perpendicular to Bli. (1mark)

B= flo ( 2 7f n I ) (1 mark)47f r

Po ( 2 1 f n l ) = BH tan e (lmark)41 f r

231



1= { 2 r B H } t a n e (1 mark)

Po n

Reduction factor

:. I = K tan e (1mark)

18 . State the tangent law in magnetism. Express it in mathematical K

terms, Recall

Easy

For a given restoring field, the deflecting field is directly

proportional to the tangent of the angle of deflection. (1 mark)

B =: BH tan e (1 mark)

19. Define the terms: (i) Declination, (ii) Magnetic dip e

Declination at a place is the angle between the geographic meridian

and the magnetic meridian. (1 mark)

Dip at a place is the angle between the earth's total magnetic field

and the horizontal drawn in the magnetic meridian. (1 mark)

K

Recall

Easy

"PUC

14.magnetic effect of electric current (physics - chapter wise question bank)

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