Physics Chapters 20-23
An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, then the magnetic field must have a component
-z axis
Two long parallel wires are placed side-by-side on a horizontal table and carry current in the same direction. The current in one wire is 20 A, and the current in the other wire is 5 A. If the magnetic force on the 20-A wire has magnitude 0.001 N, what is the magnitude of the magnetic force on the 5-A wire?
0.001 N
A wire along the z-axis carries a current of 4.9 A in the +z direction. Find the magnitude of the force exerted on a 3.3-cm long length of this wire by a uniform magnetic field pointing in the -x direction having a magnitude 0.43 T.
0.07 N
When you speak on the telephone from LA to a friend i NY 4000 km away, how long does it take your voice to travel?
1.33 E-2 s
A light ray is incident on an air to glass interface at an angle of 45 degrees and is refracted at an angle of 30 degrees to the normal. What is the index of refraction of the glass?
1.4
What is the strength of a magnetic field 4 cm from a long straight wire carrying 3.0 A of current?
1.5 E-5 T
Two long straight horizontal wires are separated by a distance of d= 0.2 m The currents are I1= 1.0 A to the right in the upper wire and I2 = 8.0 A to the left in the lower wire. What is the magnitude of the magnetic field at point P that is a distance 0.1 m below the lower wire?
1.5E-5
An electron experiences the greatest force as it travels in a magnetic field when it is moving northward. The force is upward and of magnitude What are the magnitude and direction of the magnetic field?
1.6 T, East
A flux through a coil changes from 4.0X10-5 Wb to 5.0X10-5 Wb in 0.10 s. What emf is induced in this coil by this flux?
1E-4 V
A beam of light traveling in air is incident on a slab of transparent material. The incident beam and the refracted beam make angles of 40 degrees and 26 degrees to the normal. What is the speed of light in the transparent material?
2 E-8 m/s
A 1.5-m length of wire carrying 4.5 A of current is oriented horizontally. At that point on the Earth's surface, the dip angle of the Earth's magnetic field makes an angle of 38° to the wire. Estimate the magnitude of the magnetic force on the wire due to the Earth's magnetic field of 5.5 x10-5 T at this point.
2.3 x10-4 N
Two long parallel wires carry currents of 5.0 A and 8.0 A in the same direction. The wires are separated by 0.30 m. Find the direction and the magnitude of magnetic force per unit length between the two wires.
2.7 E-5 N/m attractive
What is the wavelength for the carrier wave of 92.9 MHz?
3.2 m
Calculate the critical angle for the crown glass-air boundary. The index of refraction of glass is 1.52 .
41.4 degrees
What is the critical angle for light traveling from water (n = 1.33) into air?
48.8 degrees
Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 0.20 m. What is the strength of the magnetic field midway between the two wires?
5E-5 T
An ideal transformer has 60 turns on its primary coil and 300 turns on its secondary coil. If 120 V is applied to the primary, what is the voltage in the secondary?
600 V
An electron experiences the greatest force as it travels 1.8x106 m/s in a magnetic field when it is moving southward. The force is upward and of magnitude 2.2x10-12 N. What is the magnitude and direction of the magnetic field?
7.6 T B points West
A coil is wrapped with 15 turns of wire on a square frame with an area of 0.40 m^2. A uniform magnetic field is applied perpendicular to the plane of the coil. If the field changes uniformly from 0 to 0.75 T in 0.050 s, find the average value of the induced emf.
90 V
A person's face 30 cm in front of a concave shaving mirror. If the image is an erect image 1.5 times the size of the object. What is the focal length of the mirror?
90 cm
Jumper cables used to start a stalled vehicle often carry a 15 A current. How strong is the magnetic field 15 cm away? What percentage of the Earth's magnetic field is this (B earth = 5.5 x10-5 T)?
B= 2.0 x10-5 T 36%
A circular coil lies flat on a horizontal table. A bar magnet is held above its center with its north pole pointing down. The stationary magnet induces (when viewed from above)
No current
A bar magnet is moved rapidly toward a 40-turn circular coil of wire. As the bar magnet moves the average value of Bcos(theta) over the area of the coil increases from 0.0125 T to 0.450 T in 0.250 s. The radius of the coil is 3.05 cm and the resistance of the wire is 3.55 ohms. a) Find the change in the magnetic flux b) Use Faraday's law to find the magnitude of the induced emf. c) Find the magnitude of the induced current in the wire.
a) 0.051 Wb b) -0.204 V c) -0.066 A
Two long straight parallel wires are 15 cm apart. Wire A carries 2.0 A current. Wire B's current is 4.0 A in the same direction. (a) Determine the magnetic field magnitude due to wire A at the position of wire B. (b) Determine the magnetic field due to wire B at the position of wire A. (c) Are these two magnetic fields equal and opposite? Why or why not? (d) Determine the force on wire A due to wire B, and the force on wire B due to wire A. Are these two forces equal and opposite? Why or why not?
a) 2.7 x10-6 T b) 5.3 x10-6 T c) not equal, opposite d) 1.1 x10-5 T; equal and opposite
A model train transformer plugs into 120 V ac and draws 0.75 A while supplying 15 A to the train. a) What voltage is present across the tracks (First identify VP, IS, and Ip, and get Vs.) b) Is this a step-up (VS >VP) or step-down (VS < VP) transformer? c) What is NS if NP = 60? d) What is the power transformed?
a) 6 V b) step-down c) 3 d) 90 W
(a) What is the force per meter on a wire carrying a 9.80-A current when perpendicular to a 0.80-T magnetic field? (b) What if the angle between the wire and the field is 45.0 degrees?
a) 7.84 N/m b) 5.5 N/m
A circular hoop in the plane of the paper lies in a 0.75-T magnetic field pointing into the paper. If the loop's diameter changes from 20.0 cm to 6.0 cm in 0.50 s, a) what is the direction of the induced current, b) what is the magnitude of the average induced emf, and c) if the coil resistance is 2.5 ohms, what is the average induced current?
a) CW b) 4.3 x10-2 V c) 1.7 x10-2 A
Sunlight is observed to focus at a point 18.5 cm behind a lens. (a)What kind of lens is it? (b) What is its power in diopters (Unit for lens power. 1 diopter = 1/m) ?
a) converging b) 5.41 D
A loop lies flat on a table top in a region where the magnetic field vector points straight down. The magnetic field vanishes suddenly. When viewed from above, what is the sense of the induced current in this coil as the field fades?
clockwise
An object 3 cm high is placed 20 cm from a convex mirror with a focal length of 8 cm. Find the position of the final image and the magnification of the mirror.
di = - 5.7 cm m = 0.29
An object is placed 30 cm from a diverging lens with a focal length of 8 cm. Find the image distance and the magnification of the lens.
di = -6.32 m = 0.21
An object is placed 15 cm from a concave mirror of focal length 20 cm. The object is 4.0 cm tall. How tall is the image?
di = -60 cm hi = 16 cm
An object is placed 30 cm from a converging lens with a focal length of 8 cm. Find the image distance and the magnification of the lens.
di = 11 cm m = -0.36
A positive charge is moving East and experiences a magnetic force due north. In which direction must the magnetic field have a component?
into the page
Two long straight horizontal wires separated by a distance of d= 0.2 m are lying on the plane of a paper. The currents are I1= 1.0 A to the right in the upper wire and I2 = 8.0 A to the left in the lower wire. What is the direction of the magnetic field at point P that is a distance 0.2 m below the lower wire?
out of the plane of the paper
A long, straight, horizontal wire carries current toward the east. An electron moves toward the east alongside and just south of the wire. What is the direction of the magnetic force on the electron?
south
A wire lying in the plane of the page carries a current toward the bottom of the page. What is the direction of the magnetic force it produces on an electron that is moving to the left directly toward the wire?
to the bottom of the page
A vertical wire carries a current straight up in a region where the magnetic field vector points toward the north. What is the direction of the magnetic force on this wire?
west
