Old Exam Questions Chapter 29 (Dr. Gondal Phys102)
T081
Q10.
Two long straight wires penetrate the plane of the paper at two vertices of an equilateral
triangle as shown in
Fig 6
. They each carry 2.0 A, out of the page. The magnetic field at the third vertex (P) has
magnitude (in T): A) 1.7 × 10−5
Q12.
A long, coaxial cable, shown in cross-section in
Fig 8
, is made of two conductors that share a common central
axis, labeled
C
. The current in the
inner
conductor is 2.0 A directed
into the
page
and that in the
outer
conductor is
2.5 A directed
out of the page
. The distance from point
C
to
B
is 0.0030 m. What is the magnitude and direction of
the magnetic field at point
B
? ( Ans:
3.3 × 10–5 T, counterclockwise)
Q13
. Solenoid 2 has twice the radius and six times the number of turns per unit length as solenoid 1. Find the ratio
of the magnetic field in the interior of solenoid 2 to that in the interior of solenoid 1, if the two solenoids carry the
same current. (Ans:
6)
Fig.6, T081
Fig.8, T081
T072: Q23
.Two long parallel straight wires, at a separation d = 20.0 cm, carry currents i1 = 3.61 mA and i2 = 3.00
mA out of the page. At what distance from the origin on the x-axis shown in Fig. 1, is the net magnetic field due to
the currents equal zero? (Ans:
11 cm)
Q24.
What are the strength and direction of the magnetic field at point P in Fig. 2 at the center of arcs, if the current
in the loop is 5.0 A? (Ans: 79 μT into the page)
Q25:
A long solid cylindrical wire, of radius R = 2.00 cm carries a uniform current of 1.9 A. Find the magnetic field
strength at a distance of 1 cm from the center of the wire. (Ans:
9.5 μT)
Q27.
We wish to generate a 0.10 T uniform magnetic field near the center of a 10 cm long ideal solenoid. What is the
minimum number of turns needed, if the wire can carry a maximum current of 10 A? (Ans: 800)
T071
Q23
. Two long straight, parallel wires are 3.0 cm apart. They carry currents I1 = 3.0 A and I2= 5.0 A in opposite
directions, as shown in the figure 1. At what point, beside infinity, could the magnetic field be zero? (Ans: A)
Q24.
A cylindrical wire of radius R carries current I uniformly distributed across its cross-section.
Find the magnetic field inside the wire at r < R from the axis. (Ans:
B=
μ
0
i r/(2
π
R
2
))
Q25.
A magnetic field of 0.10 T is generated near the center of a 10 cm long solenoid. How many turns are needed
if the current in the wire is 10 A? (Ans:
796)
Q27.
What is the magnetic field at the center of the loop in the figure 2. (Ans: 2.1
⋅
10
-4
T into the page)
Fig 1, T072
Fig 2, T072
Fig 1, T071
Fig 2, T071
1