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Phy 213 Question Paper

Phy 213

Course:Bachelor Of Education In Physics

Institution: Chuka University question papers

Exam Year:2013

CHUKA UNIVERSITY

COLLEGE
UNIVERSITY EXAMINATIONS
SECOND YEAR EXAMINATION FOR THE AWARD OF DEGREE OF
BACHELOR OF SCIENCE IN COMPUTER SCIENCE)
PHYS 213: ELECTRICITY AND MAGNETISM I
STREAM: B/Ed (Sci), BSc (Gen), BSc (Comp) Y2S1 TIME: 2 HOURS
DAY/DATE: THURSDAY 4/8/2011 2.30 P.M. – 4.30 P.M.
INSTRUCTIONS:
First read carefully through the question paper then answer Question 1 (compulsory) and any other two questions only.

Useful Constants
Useful Constants and formulas

e (charge of an electron (e-)/proton(e+) =
SECTION ONE
Question One
(a) Give three properties of electric charges. [3 marks]
(b) State ohms law. [1 mark
(c) What do you understand by capacitive time constant in a RC circuit? [2 marks]
(d) What is the electric potential at the surface of a gold nucleus? The radius is and atomic number Z is 79. Assume that the nucleus is spherically symmetrical and behaves as if it’s a point charge. [2 marks]
(e) Suppose one wants to make a 0.5O resistor out of 1g of copper. If the resistor is a uniform cylinder, what is the diameter and length required? Take the density of copper to be 8.95 x 103 Kg m-3. and resistivity to be [5 marks]

fig 1.

(g) Show that the equivalent capacitance of capacitors and connected in series is . C=CC/(C+C) [3 mKS]

fig 2. [4 marks]

(H) Using Ampere’s law, show that the magnetic field inside and outside a long straight wire carrying a current, I, is directly proportional and inversely proportional to r respectively, where r is the distance from the center of the wire. [5 marks]

(I) A proton moves at 8.0 x 106 m/s along the x axis. It enters a region where there is a magnetic field of magnitude 2.5 T directed at an angle of 30° from the positive y-axis and lying in the xy-plane. What is the initial force the proton feels and what is its acceleration? [5 marks]

(J) How long does it take for 50% of the maximum charge to be deposited on the circuit below when the switch is closed? The resistor is 2 million ohms and each capacitor is 10nF. [5 marks]

Question Two
(a) State Ohm’s Law. [2 Marks]

(b) (i) Reduce the resistor combination in Fig 7 into a single-resistor equivalent circuit.
[6 marks]

(ii) Calculate the total current I delivered from the battery. [1 Mark]

(iii) Find the voltage V1 across the resistor R1. [1 Mark]

(iv) Find the current I2 flowing through R2. [2 Marks]

(v) Calculate the power dissipated in the resistor R1. [1 Mark]

Fig 7

(c) A vacuum cleaner has a rating of 11 amps. (Ratings are RMS currents). What is the maximum power consumed, when connected to 240V mains?

Question Four

(a) One straight wire carries a current of 10 Amps north and another straight wire carries a current of 5.0 Amps west. What is the direction and magnitude of the magnetic field 0.25 m above the point where the wires intersect?

Fig 8

(b) A solenoid has 100 turns and a length of 10 cm. It carries a current of 0.500 A. What is the magnetic field inside the solenoid?

(c) A proton moves at 8.0 x 106 m/s along the x axis. It enters a region where there is a magnetic field of magnitude 2.5 T directed at an angle of 30° from the positive y-axis and lying in the xy-plane. What is the initial force the proton feels and what is its acceleration?

Question Five

(i) State the Kirchoff’s Rule. What do they signify? [5 marks]
(ii) Find the current flowing through the 3O resistor in the circuit of fig 9, below using Kirchoff’s Rules. Make sure u specify direction of current [7 marks]
(iii) What are the currents in the other two resistors? [2 marks]
(iv) Find the power dissipated by the 3O resistor. [1 mark]

Fig 9.

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Phy 213 Question Paper

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