Can You Indentify the Correct Option for the Following Motional Emf Flashcards

Can you identify the correct option for the following EMF flashcards? These flashcards are quite helpful. Motional EMF as an electrical power conversion for the space shuttle is the incentive for the satellite experiment. Motional EMF occurs if the magnetic field moves and the rod is immovable relative to the earth. Read and study these flashcards and get acquainted with motional EMF.

70 cards   |   Total Attempts: 183
  

Cards In This Set

Front Back
A conducting loop of wire is placed in a magnetic field that is normal to the plane of the loop.
Which one of the following actions will not result in an induced current in the loop?

A) Rotate the loop about an axis that is parallel to the field and passes through the center of the
loop.
B) Increase the strength of the magnetic field.
C) Decrease the area of the loop.
D) Decrease the strength of the magnetic field.
E) Rotate the loop about an axis that is perpendicular to the field and passes through the center
of the loop.

Ans: A
Which of the following units are equivalent to those of motional emf?
A) T m/s
B) V m2/s
C) J/s
D) A * Ohm
E) T m
Ans: D
The figure shows a uniform magnetic field that is normal to the plane of a conducting loop
with resistance R. Which one of the following changes will cause an induced current to flow
through the resistor?
A. decreasing the area of the loop
B. decreasing the magnitude of the magnetic field
C. increasing the magnitude of the magnetic field
D. rotating the loop through 90° about an axis in the plane of the paper
E. all of the above
Ans: E
A conducting bar moves to the left at a constant speed v on two conducting rails joined at the
left as shown. As a result of the bar moving through a constant magnetic field, a current I is
induced in the indicated direction. Which one of the following directions is that of the magnetic
field?

A) toward the right
B) toward the left
C) parallel to the long axis of the bar

D) into the page
E) out of the page
Ans: E
A 1.2-kg rod that has a length of 1.0 m and a resistance of 5.0 slides with constant speed down a pair of frictionless vertical conducting rails that are joined at the bottom. Other than the rod, the rest of the circuit is resistanceless. A uniform magnetic field of magnitude 3.0 T is perpendicular to the plane formed by the rod and the rails as shown. Determine the speed of the rod. A. 0.38 m/s B. 0.90 m/s C. 2.6 m/s D. 6.5 m/s E. 8.7 m/s
Ans: D
A 0.45-m metal rod moves 0.11 m in a direction that is perpendicular to a 0.80-T magnetic
field in an elapsed time of 0.036 s. Assuming that the acceleration of the rod is zero m/s2,
determine the emf that exists between the ends of the rod.
A) 1.1 V
B) 0.27 V
C) 0.076 V
D) 9.1 × 10–5 V
E) This cannot be determined without knowing the orientation of the rod relative to the magnetic field.
Ans: E
A 0.60-T magnetic field is directed perpendicular to the plane of a circular loop of radius 0.40
m. What is the magnitude of the magnetic flux through the loop?
A) 0.049 Wb
B) 0.098 Wb
C) 0.24 Wb
D) 0.30 Wb
E) zero Wb
Ans: D
The Earth's magnetic field passes through a square tabletop with a magnitude of 4.95 × 10–5 T
and is directed at an angle of 165° relative to the normal of the tabletop. If the tabletop has 1.50-
m sides, what is the magnitude of the magnetic flux through it?
A) 1.08 × 10–4 Wb
B) 7.11 × 10–5 Wb
C) 2.88 × 10–5 Wb
D) 1.92 × 10–5 Wb
E) 3.30 × 10–6 Wb
Ans: A
A circular copper loop is placed perpendicular to a uniform magnetic field of 0.75 T. Due to
external forces, the area of the loop decreases at a rate of 7.26 × 10–3 m2/s. Determine the
induced emf in the loop.
A) 3.1 × 10–4 V
B) 6.3 × 10–4 V
C) 1.2 × 10–3 V

D) 5.4 × 10–3 V
E) 3.1 V
Ans: D
A conducting loop has an area of 0.065 m2 and is positioned such that a uniform magnetic
field is perpendicular to the plane of the loop. When the magnitude of the magnetic field
decreases to 0.30 T in 0.087 s, the average induced emf in the loop is 1.2 V. What is the initial
value of the magnetic field?
A) 0.42 T
B) 0.75 T
C) 0.87 T
D) 1.2 T
E) 1.9 T
Ans: E
A uniform magnetic field passes through two areas, A1 and A2. The angles between the
magnetic field and the normals of areas A1 and A2 are 30.0° and 60.0°, respectively. If the
magnetic flux through the two areas is the same, what is the ratio A1/A2?
A) 0.354
B) 0.866
C) 1.00
D) 1.23
E) 1.73
Ans: A
A 250-turn solenoid carries a current of 9.0 A. The radius of the solenoid is 0.075 m; and its
length is 0.14 m. Determine the magnetic flux through the circular cross-sectional area at the
center of the solenoid.

A. 1.8 × 10–5 Wb
B. 9.9 × 10–5 Wb
C. 3.6 × 10–4 Wb
D. 7.0 × 10–4 Wb
E. 2.2 × 10–3 Wb
Ans: C
A magnetic field is directed perpendicular to the plane of a 0.15-m × 0.30-m rectangular coil
consisting of 240 loops of wire. To induce an average emf of –2.5 V in the coil, the magnetic
field is increased from 0.1 T to 1.8 T during a time interval t. Determine t.
A) 0.053 s
B) 0.13 s
C) 12 s
D) 6.4 s
E) 7.3 s
Ans: E
A circular coil of wire has 25 turns and has a radius of 0.075 m. The coil is located in a
variable magnetic field whose behavior is shown on the graph. At all times, the magnetic field is
directed at an angle of 75° relative to the normal to the plane of a loop. What is the average emf
induced in the coil in the time interval from t = 5.00 s to 7.50 s?

A. –18 mV
B. –49 mV
C. –92 mV
D. –140 mV
E. –180 mV
Ans: A
What is the magnitude of the average induced emf in the loop if the magnitude of the
magnetic field is doubled in 0.4 s?
A) 0.43 V
B) 0.65 V
C) 0.014 V
D) 0.027 V
E) 0.038 V
Ans: C