IB PHYSICS: Magneic Fields, lecromagneic Inducion, Alernaing Curren 1. This quesion is abou elecromagneic inducion. In 1831 Michael Faraday demonsraed hree ways of inducing an elecric curren in a ring of copper. One way is o move a bar magne hrough he saionary copper ring. (a) Describe briefly a way ha a curren may be induced in he copper ring using a saionary bar magne. You are given he following apparaus: copper ring, baery, variable resisor, lenghs of insulaed copper wire wih connecing erminals a each end. (b) Describe how you would use all of his apparaus o induce a curren in he copper ring. copper ring (4) In he diagram below, a magneic field links a circular copper ring. The field is uniform over he area of he ring and is srengh is increasing in magniude a a seady rae. magneic field (c) (i) Sae Faraday s law of elecromagneic inducion as i applies o his siuaion. () (ii) Draw on he diagram, an arrow o show he direcion of he induced curren in he copper ring. xplain how you deermined he direcion of he induced curren. (iii) The radius of he copper ring is.1 m and is resisance is 1.5 1 Ω. The field srengh is increasing a rae of 1.8 1 3 T s 1. Calculae he value of he induced curren in he copper ring.... (Toal 13 marks) 1
. A circular coil of wire of radius r is placed in a uniform magneic field of flux densiy B. The angle beween he plane of he coil and he magneic field is θ. B r The magneic flux linking he coil is A. πr B. B. πr Bsinθ. C. πr Bcosθ. D. πr B. 3. A magneic force acs on an elecric charge in a magneic field when A. he charge is no moving. B. he charge moves in he direcion of he magneic field. C. he charge moves in he opposie direcion o he magneic field. D. he charge moves a righ angles o he lines of he magneic field.
4. This quesion is abou he force beween curren carrying wires. Diagram 1 below shows wo long, parallel verical wires each carrying equal currens in he same direcion. The wires pass hrough a horizonal shee of card. Diagram shows a plan view of he wires looking down ono he card. eye shee of card Diagram 1 Diagram (a) (b) Draw on diagram he magneic field paern due o he currens in he wire. Ouline how wo curren carrying conducors may be used o define he ampere. () (c) The card is removed and one of he wo wires is free o move. Describe and explain, he changes in he velociy and in acceleraion of he moveable wire. (Toal 8 marks) 5. A charged paricle of mass m and charge q is ravelling in a uniform magneic field wih speed v such ha he magneic force on he paricle is F. The magneic force on a paricle of mass m, charge q and speed v ravelling in he same direcion in he magneic field is A. 4F. B. F. C. F. D. 1 F. 3
6. (a) On he diagram below, draw he magneic field paern around a long sraigh curren carrying conducor. curren carrying wire The diagram below shows a coil consising of wo loops of wire. The coil is suspended verically.. cm 6. cm ach loop has a diameer of 6. cm and he separaion of he loops is. cm. The coil forms par of an elecrical circui so ha a curren may be passed hrough he coil. (b) (i) Sae and explain why, when he curren is swiched on in he coil, he disance beween he wo loops changes. When here is a curren I in he coil, a mass of.1 g hung from he free end of he coil reurns he separaion of he loops o he original value of. cm. The circumference C of a circle of radius r is given by he expression C = πr. (ii) Calculae he curren I in he coil. You may assume ha each loop behaves as a long sraigh curren carrying wire. (5) (Toal 11 marks) 7. The definiion of he uni of curren, he ampere, is based on A. he force per uni lengh on a conducor in a uniform magneic field. B. he force per uni lengh on parallel curren carrying conducors. C. he charge per uni ime delivered by a cell of e.m.f. 1. V. D. he charge passing a poin per uni ime in an elecrical circui. 4
8. Two long, verical wires X and Y carry currens in he same direcion and pass hrough a horizonal shee of card. X Y Iron filings are scaered on he card. Which one of he following diagrams bes shows he paern formed by he iron filings? (The dos show where he wires X and Y ener he card.) A. B. C. D. 5
9. The diagram shows a coil of wire ha can roae beween he poles of a magne abou he axis XY. coil Y pole of magne pole of magne N S X A curren is passed hrough he coil by means of a commuaor conneced o he ends of he coil. Wha is he posiion of he coil in he magneic field so ha is urning effec is a maximum and wha is he posiion of he coil when he curren is reversed so ha he coil roaes coninuously? plane of coil for maximum urning effec plane of coil for reversal of curren A. parallel o direcion of field parallel o direcion of field B. normal o direcion of field parallel o direcion of field C. parallel o direcion of field normal o direcion of field D. normal o direcion of field normal o direcion of field 1. When a coil is roaed in a uniform magneic field a a cerain frequency, he variaion wih ime of he induced e.m.f. is as shown below. The frequency of roaion of he coil is reduced o one half of is iniial value. Which one of he following graphs correcly shows he new variaion wih ime of he induced e.m.f.? 6
A. B. C. D. 11. The magneic flux Φ hrough a coil having 5 urns varies wih ime as shown below..5. 3 / 1 Wb 1.5 1..5 The magniude of he e.m.f. induced in he coil is. 1 3 4 5 3 / 1 s 7
A..5 V. B..5 V. C. 5 V. D. 1 V. 1. A resisor is conneced in series wih an alernaing curren supply of negligible inernal resisance. The peak value of he supply volage is Vo and he peak value of he curren in he resisor is I. The average power dissipaion in he resisor is A. B. V I V I C. V I. D. V I. 13. A magneic field links a closed loop of meal wire. The magneic field srengh B varies wih ime as shown. B 1 3 A curren is induced in he loop during he ime period A. 1 only. B. only. C. and 3 only. D. 1 and 3 only. 8
14. Faraday s law of elecromagneic inducion saes ha he induced e.m.f. is A. proporional o he change in magneic flux linkage. B. proporional o he rae of change of magneic flux linkage. C. equal o he change in magneic flux linkage. D. equal o he change of magneic flux. 15. The diagram below shows he variaion wih ime of he e.m.f. generaed in a coil roaing in a uniform magneic field. e e T T 3 T Wha is he roo mean square value rms of he e.m.f. and also he frequency f of roaion of he coil? rms A. e B. e C. e f T 1 T T D. e 1 T 9
16. The norh pole of a permanen bar magne is pushed along he axis of a coil as shown below. axis of coil N S V The poiner of he sensiive volmeer conneced o he coil moves o he righ and gives a maximum reading of 8 unis. The experimen is repeaed bu on his occasion, he souh pole of he magne eners he coil a wice he previous speed. Which of he following gives he maximum deflecion of he poiner of he volmeer? A. 8 unis o he righ B. 8 unis o he lef C. 16 unis o he righ D. 16 unis o he lef 17. This quesion is abou elecromagneic inducion. A small coil is placed wih is plane parallel o a long sraigh curren carrying wire, as shown below. curren carrying wire small coil (a) (i) Sae Faraday s law of elecromagneic inducion. () (ii) Use he law o explain why, when he curren in he wire changes, an e.m.f. is induced in he coil. The diagram below shows he variaion wih ime of he curren in he wire. 1
curren magneic flux e.m.f (b) (i) Draw, on he axes provided, a skech graph o show he variaion wih ime of he magneic flux in he coil. (ii) (iii) Consruc, on he axes provided, a skech graph o show he variaion wih ime of he e.m.f. induced in he coil. Sae and explain he effec on he maximum e.m.f. induced in he coil when he coil is furher away from he wire. () () (c) Such a coil may be used o measure large alernaing currens in a high volage cable. Idenify one advanage and one disadvanage of his mehod. Advanage: Disadvanage: () (Toal 1 marks) 11