University of Bahrain College of Science Dept. of Physics PHYCS 102 FINAL EXAM

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1 Unversty o Bahran College o Scence Dept. o Physcs PHYCS 10 FINAL XAM Date: 15/1/001 Tme:Two Hours Name: ID# Secton: Q1. For the set o three charges shown below, 10µC an 0.3m, n: a) The electrc el at the center (O). y b) The electrc potental at the center (O). + 6 x 0, y ( ) K 10 N / C - - x O K K + K K 3 x 10 5 Q. In the gure shown below, two pont charges, Q nc an Q -4.0 nc, are separate by 30.0 cm. a) What s the potental energy o the par? Q -4nC a 18cm Q 1 +6nC b) What s the electrc potental erence ab? x x 1c Q Q 7 U K 7. x J cm 9 6 x 10 4 x 10 a K x 10 4 x 10 K a - b b + 63 b Q3. A pont charge +9 µc s locate 4m rom an nnte lne o unorm charge per unt length λ -7 µc/m. Fn: a) The electrc el at pont p. λ b) The electrc orce on charge. p r p x F m

2 λ K πε () o 83. x 10 3 N/C ( ) p + λ F. πεo(4) 0.8 N (attracton ) Q4. In the gure shown below, the magntue o r s x 10 4 N/C an the cube has a se o a 0.1m, n each o the ollowng cases etermne the electrc lux through the shae ace o the cube. 37 o x (1) () (3) ( r s to the rght) ( r s upwars) ( r at an angle o 37 o ) Φ A N. m 00. C Φ 0 π θ N. m C o Φ A cos 37 Q5. A sphercal conuctor has a raus o 1cm an charge o 30nC. Calculate : a) The electrc el at center O an at pont p 0 cm rom O. b) The potental erence op. p p Q30nc o 9 30 x 10 0, p k 6.75 (0.) Q Q op bp K K r p 900 x 10 3 N C O 1c bb r p 0cm

3 Q6. An ar-lle capactor conssts o two parallel plates, each wth an area o 7.5 cm, separate by a stance o 1.6 mm. The capactor s charge to a potental erence o 100 volt, then s remove rom the source. a) Calculate the electrc el between the plates. b) I the plates were pulle apart such that ther separaton becomes 3. mm, what woul be the voltage across the plates? c) The space between the plates o capactor (n part a) s lle wth a electrc substance o electrc constant K.5. What s the voltage across the plates? 6.5K / m x 10 Q Q, C C 00, εoa εoa c. Q Q ε, oa ε oak, 40 K 1 15 kω Q7. In the crcut shown, n: a) The currents n 1, an 3. C10 µf b) The charge on capactor C. 5 kω ε 0 I 0 1 ma 3 0 x 10 I 1 I 1 ma, I kΩ c I 5, Q C c 50 µ C

4 Q8. A copper wre o m n length has a cross secton area.5 (mm) carres a current o 5A. The ensty o ree electrons s.8 x 10 9 m -3. Compute: a) The rt velocty o the electrons. b) The potental rop along the wre. Use ρ 1.7 x 10-8 Ω.m. ν J ne x /.5 x x 10 x 1.6 x10 m / s ρl x 10 Ω, I 6.88 x 10 A or 5 L ρj L 1.7 x 10 x x 6.88 x 10.5 x 10 8 Q9. In the crcut shown, the current was oun to vary accorng to the ollowng relaton where I s n µa: I(t) 0 e t/10 (µa). I C µf, n: a) The values o ε an b) The charges that passes through the crcut urng 0s. ε C µf t / C I ε e C 10S 5MΩ Q 0S t /10 [ e ] 0S t / µ C It x 10 e t 00 x 10 0 O o Q10. Two long, parallel wres carry currents I 1 3.0A an I 3.0A, both recte nto the gure gven below. Determne the magntue o the resultant magnetc el at pont p. 5.0 cm µ I1 B1 10 x 10 π o ( 0.05) µ I B o 50 x 10 T π ( 0.1) T I cm B r 1 1 B B1 + B 130 x 10 T I B 1.0cm B r

5 Q11. A wre (mass 50g, length 40 cm) s suspene horzontally by two vertcal wres whch conuct a current I 8A as shown n the gure below. The magnetc el n the regon s nto the paper an has a magntue o 60 mt. What s the tenson (n N) n both wres? T mg + IBL T N T I T B L mg IBL Q1. An electron wth knetc energy 1.9 x j crcles n a plane perpencular to a unorm magnetc el. The orbt raus s 5 cm. Fn: a) The magnetc el B. b) The reuency o crclng. K 1 m v, v K / m.05 x 10 7 m / s mv 4 B 4.67 x 10 T r ω v v π, 1.31 r πr 7 x 10 HZ Q13. A porton o a complete electrc crcut s shown n ths agram. The current n some resstors are gven, current n others must be oun. What s the potental erence between ponts (a) an (b). 1A ε 1 6A a c + b 3Ω Ω 1Ω A 4 Ω 1 Ω 3A ac 3, b 1 x 6 6, c ab ac c b 3x (1)

6 Q14. A soleno 3.55 cm n ameter an 1.3m n length has 850 turns an carres a current o 4.6A. Fn: a) The magnetc el at ts center. b) The average magnetc lux through ts cross secton. 850 B µ oni 4π x mT Φ BA (4x10 ) π ( 3.55/ ) 4 [ x 10 ] 39.6 x10 Wb Q15. A rectangular conucton loop o area A 0.0 m an resstance 0.1 Ω. A tme varyng magnetc el n a recton perpencular to the plane o the loop s gven by the euaton: B (t) 0. cos (100πt) (T) Fn: a) The nuce em n the loop as a uncton o tme. b) The maxmum value an recton o nuce current n the loop. Φ BA 0.004cos( 100 πt) Φ ε ( 0.004) (100π ) Sn (100πt ) t 0.1 Ω 1.5 sn (100πt) ε 1.5sn(100πt I A B r I max 1.5A Inuce current s alternatve (A.C) Use the ollowng terms: K 9x10 9 N.m /C ε o x 10-1 C /N.m, m e 9.1 x Kg m p 1.67 x 10-7 Kg e 1.60 x C g 10 m/s N A 6.0 x 10 3 mol -1 µ o 4π 10 Τ.m/Α