Partial preview of the text
Download Current electricity model question and more Study notes Physics in PDF only on Docsity!
perpendicular 10 (0 =0°). ‘ (bh) When the plane of IC parallel to the magne (a direction as t es it. M conduct Ww to unio! il em. Where, N - section, | 11. Give the « an induc Ans: (/ = ~ iF Where L is and liscu 12. How doe depend o Ans: Directly p number of 3 he On what Ans: Electrome 14. Define § Ans: Self indus of emt is through t TWO MARK 15. State - gtectre Ans; (i) The is eq flux ine eml (Q)) Ans: Self-Induction a Piitnescsi i which an | emf is induced ina coil due to the change in — ~ Magnetic flux through the coil as a result of | oe variation of current in the same coil, 10. Menti on” the — expression for self inductance ofa solenoid, Give the meaning ofthe symbols used. (EQ) Ans: ; . Hohl, Nod vd Where, N - Number of turns, A+ Area of cross section, 7+ length of a solenoid 11, Give the expression for energy stored in an inductance coil carrying current, (EQ) Ans: v=) 77? ) - Where L is the coefficient of self-inductance, and lis current, 12. How does the self-inductance of a coil depend on the number turns in the coil? (M-19) Ans: Directly proportional to the square of the number of turns 13. On what principle AC generator works? (EQ) Ans: Electromognetic induction. 14. Define $1 un't of inductance (or henry). | (EQ) Ans: Sel! inductance of a coil is said to be 1H if 1V of emf is induced in a coil when the current through the coil changes at the rate of 1 As!. re a , ae ] -QUESTION 15. State and explain Faraday’s law of _ electromagnetic induction. (M-16, 17, 18) Ans; (i) The magnitude of induced emf ina circuit is equal to time rate of change of magnetic flux through the circuit. [fdd, is the change in magnetic flux in time dt then induced emis Ans The induced circulating currents produce We a metal due to the changes in magnetic flux ee linked with it are called eddy current. | Any one application: (1) Induetion furnace, (2) Speedometer (3) Dead beat palvanometer (4) Klectromapnetic breaks. a. | o 17, Mention two methods of reducing eddy ie os current, (EQ) ‘ Ans: lddy current can be minimized by (1) Using a set of laminated metal sheets of single metal black, (2) Using slotted metal sheets instead of whole metal sheets. (3) The laminations are separated by an insulating material, What is meant by Self inductance and Mutual Inductance? (}-16) Ans: Self-inductance of a coil is numerically equal to the emf induced in the coil when the current in it changes at the rate of one ampere per second, Mutialinductance of two coils is equal to the emf induced in the secondary coil when the current through the primary cail is changing at the rate of one ampere per second 19. The magnetic flux linked with a coil varies as >= 3U + 4b4 9 Find the magnitude of the emf indueed att © 28. (J?) Ans Se 4 Ate 9 il PUC - Physics (3)When the current carrying or maiae r rest near the second coil no deflection observed in the galvanometer It shows that the change in magnetic flux. responsible for production of electric current in the coil, 27. Derive an expression for motional emf, induced across the ends of a conducting rod moving perpendicular to uniform Ans. Let ‘PQ’ represent a conductor moving with a speed ‘v’ at right angles to the magnetic flux density ‘B’ pointing perpendicular to the sheet of paper and pointing towards the paper. Let RQ = x be the distance covered by the conductor. Magnetic flux @, = Blx. d(o,)_ d yi =——(Blx Inducedemf, ¢ er mk ) dx ‘ Le, ¢= —Bl— Ree edt i But, ak dt “ 8=Blv ule) Note: The Lorentz force acts on a charge in a conductor and acts along PQ. Work done in moving a charge ‘q’ from P to Q is We (Lorentz force) (displacement of the charge ‘q’) i.e, W=(Bqv)/ 8 v by definition electric p.d = ae a = Byl 7 vn (2) Equation (1) and (2) are identical. emf induced in the coil when changes at the rate of one Its SI unit is henry, let dV Phe the work done in establishing a current | in the coil a a time dt, : then dW = ~eldt is (1) Where, € is the induced emf . a a K But we have, e== | ro(s , 0 2 wf 5) 2 This work done is stored as a magnetic potential energy in an inductor, v= tur ~ By | FIVE MARKS QUESTIONS: 29. Give the principle on which AC generator works. With the schematic diagram explain the basic parts of the ac generator. Ans. AC penerator works on the principle of electro magnetic induction, The AC generator consists of the following parts: => e=6,sinot Where ¢, = NBA® = e eli field of Sty fanece of 7() )). Makes ay in MMagnetic field r "i in it. (M T of radius fed about angular s; Hiform horizon: ude Bx 10°, ( if the coil is 15 ¢ irrent induced (b) Mean or average a . ‘ 7 a | Fa 7 us (c) RMS value of AC — Vv : VV. =—~1..=7 eat ior (d) Instantaneous vai voltage. (e) Inductive reactan (f) Capacitive reacts (g) Impedance of LC A= R’+(X.- : i Sate (h) tano=—~> ONE MARKS QUES 1. Whatis an aite Ans: Analternating ¢ amplitude vari 
