## Tuesday, March 30, 2010

### Block test paper 1 cont

7. Upper wire produces B(IN) of higher strength in order XYZ. The lower wire produces B(out) of higher strength in order ZYX. Hence in the middle Y , B = 0 . At X ,B (IN) and at Z , B(out) .
8. The U magnet pulled up by 0.2 g force hence the wire pulled down by 0.2g force (by action reaction). Hence F direction down , B to the right , and current into page. : A
9.Current is opposite direction the wires repel each other. Hence the force is away from each other but with the same magnitude. : C
10. The clockwise gives B(IN) and anti gives B(OUT) but clockwise stronger due to radius smaller hence B(IN) is the resultant. : D
11. Cross (into) page is always at right angle to any orientation on the page itelf. Hence F= BIL where angle is 90 degrees.: A
12. Bqv = mv2/r gives r = mv/qB. Hence inversely proportional to B.
13. induced e.m.f = change in NBA/time taken. Hence E= 80x0.5x50 mT/2.5s = 800mV: C
14. square 5 x1+ square 2x5/6. Square root the answer.:C
15. Peak power = 54W. Use P=V2/R , you get peak voltage. Vo = 4.2V:C