The forces on the two vertical sides of the coil are equal and opposite.

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Cecily Phillips
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1 Q1. The diagram shows a vertical square coil whose plane is at right angles to a horizontal uniform magnetic field. current, I, is passed through the coil, which is free to rotate about a vertical axis OO'. Which one of the following statements is correct? The forces on the two vertical sides of the coil are equal and opposite. couple acts on the coil. No forces act on the horizontal sides of the coil. If the coil is turned through a small angle about OO' and released, it will remain in position. Q2. n α particle and a β particle both enter the same uniform magnetic field, which is perpendicular to their direction of motion. If the β particle has a speed 15 times that of the α particle, what is the value of the ratio? Page 1 of 12

2 Q3. The magnetic flux, Ф, through a coil varies with time, t, as shown by the first graph. Which one of the following graphs, to, best represents how the magnitude,, of the induced emf varies in this same period of time? Q4. Which line, to, correctly describes the trajectory of charged particles which enter, at right angles, (a) a uniform electric field, and (b) a uniform magnetic field? (a) uniform electric field circular circular parabolic parabolic (b) uniform magnetic field circular parabolic circular parabolic Page 2 of 12

the plane of the coil through Z Q6. coil, mounted on an axle, has its plane parallel to the flux lines of a uniform magnetic field, as shown.

3 Q5. The diagram shows a square coil with its plane parallel to a uniform magnetic field. Which one of the following would induce an emf in the coil? movement of the coil slightly to the left movement of the coil slightly downwards rotation of the coil about an axis through XY rotation of the coil about an axis perpendicular to the plane of the coil through Z Q6. coil, mounted on an axle, has its plane parallel to the flux lines of a uniform magnetic field, as shown. When a current I is switched on, and before the coil is allowed to move, there are no forces due to on the sides PQ and RS. there are no forces due to on the sides SP and QR. sides SP and QR attract each other. sides PQ and RS attract each other. Page 3 of 12

4 Q7. Particles of mass m carrying a charge Q travel in a circular path of radius r in a magnetic field of flux density with a speed v. How many of the following quantities, if changed one at a time, would change the radius of the path? m Q v one two three four Q8. The diagram shows a square coil with its plane parallel to a uniform magnetic field. Which one of the following would induce an emf in the coil? movement of the coil slightly to the left movement of the coil slightly downwards rotation of the coil about an axis through XY rotation of the coil about an axis perpendicular to the plane of the coil through Z Page 4 of 12

5 Q9. Protons, each of mass m and charge e, follow a circular path when travelling perpendicular to a magnetic field of uniform flux density. What is the time taken for one complete orbit? Q10. The magnetic flux through a coil of N turns is increased uniformly from zero to a maximum value in a time t. n emf, E, is induced across the coil. What is the maximum value of the magnetic flux through the coil? E t N Page 5 of 12

6 Q11. section of current-carrying wire is placed at right angles to a uniform magnetic field of flux density. When the current in the wire is I, the magnetic force that acts on this section is F. What force acts when the same section of wire is placed at right angles to a uniform magnetic field of flux density 2 when the current is 0.25 I? F 2F Q12. The magnetic flux through a coil of 5 turns changes uniformly from Wb to Wb in 0.50 s. What is the magnitude of the emf induced in the coil due to this change in flux? 14 m V 16 m V 30 m V 80 m V Page 6 of 12

7 Q13. vertical conducting rod of length l is moved at a constant velocity v through a uniform horizontal magnetic field of flux density. Which line, to, in the table gives a correct expression for the induced emf for the stated direction of the motion of the rod? direction of motion induced emf vertical horizontal at right angles to the field lv vertical lv horizontal at right angles to the field Page 7 of 12

8 Q14. rectangular coil is rotated in a uniform magnetic field. When the coil is rotated at a constant rate, an alternating emf ε is induced in it. The variation of emf ε, in volts, with time t, in seconds, is given by ε = 20 sin (100 πt) Which line, to, in the table gives the peak value ε 0 and the frequency f of the induced emf? ε 0 / V f / Hz Page 8 of 12

Q15. horizontal straight wire of length 40 mm is in an east-west direction as shown in the diagram. uniform magnetic field of flux density 50 mt is directed downwards into the plane of the diagram.

9 Q15. horizontal straight wire of length 40 mm is in an east-west direction as shown in the diagram. uniform magnetic field of flux density 50 mt is directed downwards into the plane of the diagram. When a current of 5.0 passes through the wire from west to east, a horizontal force acts on the wire. Which line, to, in the table gives the magnitude and direction of this force? magnitude / mn direction 2.0 north 10.0 north 2.0 south 10.0 south Q16. Which line, to, in the table correctly describes the trajectory of charged particles which enter separately, at right angles, a uniform electric field, and a uniform magnetic field? uniform electric field uniform magnetic field parabolic circular circular parabolic circular circular parabolic parabolic Page 9 of 12

10 M1. M2. M3. M4. M5. M6. M7. M8. Page 10 of 12

11 M9. M10. M11. M12. M13. M14. M15. M16. Page 11 of 12

12 Page 12 of 12

Phys222 Winter 2012 Quiz 4 Chapters 29-31. Name

Phys222 Winter 2012 Quiz 4 Chapters 29-31. Name Name If you think that no correct answer is provided, give your answer, state your reasoning briefly; append additional sheet of paper if necessary. 1. A particle (q = 5.0 nc, m = 3.0 µg) moves in a region