1. A horizontal compass is placed 18 cm due south from a straight vertical wire
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Question
1. A horizontal compass is placed 18 cm due south from a straight vertical wire carrying a 43-A current downward. Assume the horizontal component of the Earth's field at this point is 0.45×10?4 T and the magnetic declination is 0?.
In what direction does the compass needle point at this location?
In what direction does the compass needle point at this location?
2. An electron experiences the greatest force as it travels 2.2×106m/s in a magnetic field when it is moving northward. The force is vertically upward and of magnitude 8.6×10?13N.
a) What is the direction of the magnetic field?
b) What is the magnitude of the magnetic field?
B = _______ T
3. Find the direction of the force on a negative charge for each diagram shown in the figure, where v? (green) is the velocity of the charge and B? (blue) is the direction of the magnetic field. (? means the vector points inward. ?means it points outward, toward you.) (Figure 1)
a) diagram (a)
b) diagram (b)
c) diagram (c)
d) diagram (d)
e) diagram (e)
f) diagram (f)
4. Alpha particles (charge q = +2e, massm = 6.6×10?27kg) move at 1.3×106 m/s .
What magnetic field strength would be required to bend them into a circular path of radiusr = 0.24 m ?
B = ________ T
5.
a) Determine the magnetic field midway between two long straight wires 2.0 cm apart in terms of the current I in one when the other carries 25 A.Assume these currents are in the same direction.
d. Bnet=(2.0×10?5T/A)(I+25A)
b) Determine the magnetic field midway between two long straight wires 2.0 cm apart in terms of the current I in one when the other carries 25 A.Assume these currents are in opposite directions.
6. A 31.0-cm long solenoid 1.25 cm in diameter is to produce a field of 4.50 mT at its center.
How much current should the solenoid carry if it has 960 turns of the wire?
I= _______________
7. A Hall probe, consisting of a rectangular slab of current-carrying material, is calibrated by placing it in a known magnetic field of magnitude 0.12 T . When the field is oriented normal to the slab's rectangular face, a Hall emf of 15 mV is measured across the slab's width. The probe is then placed in a magnetic field of unknown magnitude B, and a Hall emf of 70 mV is measured. Determine B assuming that the angle ?between the unknown field and the plane of the slab's rectangular face is
a) ? = 90?.
B = ______ T
b) ? = 60?.
B = ______ T
8. The magnetic force per meter on a wire is measured to be only 29 % of its maximum possible value.
Calculate the angle between the wire and the magnetic field.
? = ____ ?
9. The force on a wire is a maximum of8.50×10?2 N when placed between the pole faces of a magnet. The current flows horizontally to the right and the magnetic field is vertical. The wire is observed to "jump" toward the observer when the current is turned on.
a) What type of magnetic pole is the top pole face?
() South pole
() North pole
b) If the pole faces have a diameter of 19.0 cm , estimate the current in the wire if the field is 0.460 T .
I= __________
c) If the wire is tipped so that it makes an angle of 15.0 ? with the horizontal, what force will it now feel? [Hint: What length of wire will now be in the field?]
Frotated = _____________
10. A compass needle points 19 ? E of N outdoors. However, when it is placed 13.0 cm to the east of a vertical wire inside a building, it points 35 ? E of N. The Earth's field is the same at both positions of the compass, it is 0.50×10?4T and is horizontal.
a) What is the magnitude of the current in the wire?
I= ________
b) What is the direction of the current in the wire?
11.
a) Determine the magnitude of the force on an electron traveling 6.85×105 m/s horizontally to the east in a vertically upward magnetic field of strength0.35 T .
Fmax=__________
b) Determine the direction of the force on an electron.
12. A long metalic strip 1.8?cm wide and 1.0?mm thick is placed in a 1.4-T magnetic field as in the (Figure 1) . When a steady current of 16 A passes through it, the Hall emf is measured to be 1.02 ?V.
a) Determine the drift velocity of the electrons.
vd =_________
b) Determine the density of free (conducting) electrons (number per unit volume) in the copper.
n = _________
13. Determine the magnitude and direction of the force between two parallel wires 15 m long and 4.0 cm ? apart, each carrying 15 A in the same direction:
14. The force on a wire carrying 7.45 A is a maximum of 2.38 N when placed between the pole faces of a magnet.
If the pole faces are 57.5 cm in diameter, what is the approximate strength of the magnetic field?
B = _______________ T
15. A power line carries a current of 95 A west along the tops of 8.5-m-high poles.
a) What is the magnitude of the magnetic field produced by this wire at the ground directly below?
B = _______________ T
b) What is the direction of the magnetic field produced by this wire at the ground directly below?
() east
() south
() west
() north
c) How does this compare with the Earth's magnetic field of about 1/2 G?
d) Where would the wire's magnetic field cancel the Earth's field?
d = __________ m below the wire
a. south of west b. south of east c. north of east d. north of westExplanation / Answer
1) direction does the compass needle point at this location - north of east
2) a) the direction of the magnetic field = east
b) magnitude of the magnetic field = 8.6×1013/(1.6 * 10-19 *2.2×106)
= 2.443 T
3) a) left
b) left
c) upwards
d) inward into the screen
e) no force
f) downwards
4) magnetic field = ( 6.6×1027 * 1.3×106)/( 2 * 1.6 * 10-19 * 0.24)
= 0.17875 T
5) a) Bnet=(2.0×105T/A)(I25A)
b) Bnet=(2.0×105T/A)(I+25A)
6) I = (0.31 *4.50 * 10-3)/( 4 * 3.14 * 10-7 * 960)
= 1.157 A
7) a) B = 0.56 T
b) B = 0.646 T
8) angle between the wire and the magnetic field = sin-1(0.29)
= 16.85 degree
9) a) Top is the South pole face
b) I = (8.50×102 )/(0.460 * 0.19)
= 0.972 A
c) Frotated = 8.50×102 * cos15
= 8.21×102 N
10) a) 0.50 x 10-4 /sin 145 = B/sin16
=> B = 0.25 * 10-4 T
=> Current = 0.25 * 10-4 * 0.13/2 * 10-7
= 16.25 A
b) west
11) F = 1.6 * 10-19 * 6.85×105 * 0.35
= 3.836 * 10-14 N
Direction = north
12) a) drift velocity = (1.02 * 10-6 * 10-3/1.4 * 1.8 * 10-5)
= 4.047 * 10-5 m/sec
b) density of free (conducting) electrons = (16 * 1.4)/(1.02 * 10-6 * 1.6 * 10-19 * 10-3)
= 13.725 * 1028 /m3
13) Force = (2 * 10-7 * 15 * 15 * 15)/0.04
= 0.0168 N
Direction = The force on each wire will be attractive.
14) strength of the magnetic field = 2.38/(7.45 * 0.575)
= 0.555 T
15) magnitude of the magnetic field = 10(-7) * 2 * 95/8.5 = 2.2 * 10-6 T
Direction = south
B / B(earth) = (0.022 G)/(0.5 G ) = 0.044
5.0 * 10-5 T = 2.0x10-7 * 95/r
=> d = 0.38 m
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