Electromagnetic Induction Questions and Answers

An unloaded bus can be stopped by applying brakes on straight road after covering a distance x Suppose the passenger add 50 of its weight as the load and the braking force remains unchanged how far will the bus go after the application of the brakes Velocity of bus in both case is same Consider negligible friction 1 Zero 2 1 5 x 3 2x 4 2 5 x

23 A wire of length 1 m is moving at perpendicular to its length and a homogeneous magnetic field of 0 5 T The ends of the wire are joined to a circuit of resistance 6 2 The rate at which work is being done to keep the wire moving at constant speed is 1 7 2 12 13 3 W W 2 W 4 1 W 28 In bri

Illustration 4 A coil is placed in a constant magnetic field The magnetic field is parallel to the plane of the coil as shown in figure Find the emf induced in the coil B

1 100 2 50 Two identical coaxial circular loops carry a current in each circulating in the same direction If the loops approach each other 1 Current in each will decrease 3 The current in each will remain same CR Circuit is 2 Current in each will increase 4 Current will increase in one and decrease in other

5 In the figure the steady state current through the inductor will be 5v V 1 2 A 3 1 25 A 4Q wwwww voo 19 3 mH 2 1 A 4 Zero 4 F

A metallic cylindrical rod PQ of resistance R slides without friction on a rectangular circuit composed of perfectly conducting wires fixed on inclined plane as shown in the figure A vertical magnetic field B exists in the region of the above mentioned setup Find the velocity of the rod PQ when it starts moving without any acceleration

1 A bar magnet is released from rest along the axis of a very long vertical copper tube After some time the magnet di 1 Will stop in the tube 2 Will move with a constant speed 3 Will move with constant acceleration 4 Will oscillate

17 A semicircular loop of radius R is rotated with an angular velocity perpendicular to the plane of a magnet field B as shown in the figure Emf induced in the loop is 1 BwR 35 BWR 3 R X X a X 2 4 X X X X X x B X 1 2 BwR BwR 4

When a loop moves towards stationary magnet with speed v induced emf in the loop is E If the magnet also moves away from the loop with the same speed then the emf induced in the loop is 1 E 2 2E 3 E 2 4 zero

In a step up transformer the turn ratio is 1 2 A leclanche cell e m f 1 5 V is connected across the primary The voltage across the secondary is 1 3 0 V 2 0 75 V 3 Zero 4 1 5 V

B I U abe X X A Y A Paragraph Styles On a separate sheet complete the following FIVE transformer problems showing ALL of your work details and UNITS All work must be properly identified and neatly prepared Put your name class and date NEATLY at the top of the sheet Submit a copy of your work along with your completed worksheet and lab summary 1 You are planning a trip to Singapore Your travel agent gives you the proper transformer to step down the voltage so you can use your electric appliances there Curious you open the case and find that the primary coil has 46 turns and the secondary has 24 turns Assuming the output voltage is 120 volts what is the standard household voltage in Singapore

are pretty much evenly distributed among the chapters except for Good luck everyone and as before you may consult any resources you may think of during this one hour time period You don t have to turn in any scratch work as most questions are conceptual Any concern Email me Ms D Question 20 Figure 1 Core Type Transformer With the specific variables mentioned below what is the number of secondary loops NS of the transformer Primary voltage rms Vp 220 V Np 200 secondary voltage Vs 1100 V 220 O 2200 800 1 pts

A bar magnet is let fall toward the center of a conducting loop of wire with the north pole oriented downward Viewed from the same side of the loop as the magnet as the north pole approaches the loop what is the direction of the induced current O Counterclockwise O Clockwise zero O Parallel to the length of the magnet

2 A 5 00 m straight conductor carries a current of 15 0 A through a uniform magnetic field The magnitude of the force on the conductor is 0 67 N The angle between the current and the magnetic field is 50 0 What is the magnitude of the magnetic field COBJ 8 3

x x x x V 0 X X VX X X X X XX X XX X X X X 4 0 V O 7 5 V X X 5 0 V X 80 cm long metal rod rotates about a fixed point at a constant rate or frequency of 5 0 ev s What will be the average emf between its ends due to the magnetic field B 0 3 2 X X X

12 45 R A 50 cm long metal rod moves along the two rails in a plane of the circuit shown and is placed perpendicular to the magnetic field indicated by x B 0 15 T If R 4 0 ohm and a constant force of 7 4 mN is needed to maintain the uniform speed v of the rod what would be this uniform speed 3 76 m s O 5 26 m s O 1 16 m s O 4 90 m s

X X X X X X X X X X X X X X X X x x x x V 0 X X X X X X X X O 12 57 m s O 11 89 m s O 25 13 m s X X le X X X X X Rod X X X X X X X A 80 cm long metal rod rotates about a fixed point at a constant rate or frequency of 5 0 rev s What should be the average linear speed v of the rod in a plane perpendicular to B that contributes to the average emf between its ends Vx X X X

R 20 A 5 0 mA 15 mA Enx A 50 cm long metal rod moves along the two rails in a plane of the circuit shown and placed perpendicular to the magnetic field indicated by x B 0 15 T If R 3 0 ohm and the uniform speed v 2 0 m s what is the induced current l O 0 05 A X X X X

Question 25 A 40 loop circular coil has a radius of 5 0 cm It is placed in a magnetic field so that the field lines from a permanent magnet B make 60 angle with the plane area of the coil If the magnet is brought toward the loop so its magnetic field varies from 0 1 T to 0 35 T in 2 microsecond the induced magnetic field is 2 0 x 106 V O 3 40 x 1011 V O 4 1 x 1014 V 1 pts 3 40 x 104 V

Good luck everyone and as before you may consult any ources you may think of ing this one hour time period You don t have in any scratch work as most questions are conceptual Any concern Email me Ms D Question 11 An AC generator with ten turns of wire each having area A 0 08 m and having a total resistance of 12 0 2 The coil rotates in a magnetic field of 0 500 T at a constant frequency f 70 0 Hz with axis of rotation perpendicular to the direction of the magnetic field What would be the maximum induced current O 14 7 A O 12 8 A O 11 9 A 30 5 A 1 pts

13 A 9 2 m length of conducting wire is formed into a square and placed in a uniform magnetic field The square is then rotated continuously in three dimensions so that the angle p between the normal to the square and the magnetic field varies between 0 and 90 The maximum magnetic flux through the conductor is 1 8 Wb What is the strength of the magnetic field 0 34 T 1 7 T 0 88 T 17 T

5 A circular coil has an area of 0 0100 m and consists of 200 turns of copper wire Initially a 1 1 T uniform magnetic field passes perpendicularly to the plane of the coil The initial magnetic field is directed into the page The field then changes The final magnetic field is O T If the field changed in 0 100 s what is the emf induced in the coil If the resistance of the coil is 2 00 2 what is the magnitude and direction of the current in the coil

7 Calculate the self inductance of a small solenoid 0 050 m long composed of 10 loops of wire with an area of 1 0 x 10 m If the current in this solenoid decreases at a rate of 0 15 A s what will the induced emf be

2 A loop with radius 0 025 m has 20 turns and a resistance of 0 500 2 A magnetic field perpendicular to the coil is B 0 050t 0 030t where B is in Teslas and t is in seconds Find the current in the loop when t 10 0s

ANSWER ANSWER ANSWER esistor after 5 s on the capacitor after 5 s 7 The figure below shows a piece of insulated wire The upper loop has a radius of 4 00 cm the middle loop has a radius of 20 cm and the lower loop has a radius of 3 00 cm The wire has a uniform resistance per unit length of 2 00 Ohm m The wire lies in a plane that is perpendicular to a uniform magnetic field directed into the page the magnitude of which is increasing at a constant rate of 3 00 T s a Find the magnitude of the induced emf b Find the magnitude of the induced current in the wire c Find the direction of the induced current in the wire ugh the resistor pacitor after the switch is closed O R 10 MegaOhm C 3 00 microFar O

Problem 1 A low pass filter for voltage can be created as shown For any input AC voltage amplitude V the output voltage Vab will be a strong function of frequency w Set the resistance to 1202 and the capacitance to 100 F and plot the ratio Vab V as a function of w over the range 0 w V 2000 rad s Label your plot with the value of the voltage ratio at w 0 and with the frequency w 2 at which the voltage ratio is half of its value at zero frequency Write that latter label with a numerical value with proper units Note that the voltage ratio Vab V involves a magnitude because the voltage amplitude Vab will be a complex number This problem and the next one will really make use of the complex impedance rules M R

one 1kQ completes a rectangular loop of a single wire The loop has an area of 0 27 m As shown there is a magnetic field coming out of the plane of the loop The magnetic field undergoes an increase over time of 32 3 T s What is the magnitude and direction of the current as it passes through the resistor created by the change in magnetic field per time 8 36 A right to left in resistor 8 72 mA left to right in resistor 8 72 mA right to left in resistor 8 36 A left to right in resistor

A uniform magnetic field is present in a cylindrical region It starts changing at a constant rate A conducting wire loop is placed symmetrically as shown O O X X X X X X X X Electric field in the loop wire will be conservative c Conducting wire loop Click to zoom Electric field in the loop wire will be non conservative only O There will be no electric field in loop wire Electric field in the loop wire will be conservative as well as non conservative

12. Which of the following would step-down the voltage that comes in to a transformer? Select all that apply. the primary coil and the second coil have the same number of turns the primary coil has less turns that the primary coil the primary coil has more turns than the secondary coil

9. A current is induced as it moves through a magnetic field. What would happen to the current if it were to be moved through a stronger magnetic field? the induced current will increase the induced current will decrease there is not enough information to say the induced current will stay constant

3. Which of the following states the Faraday's Law? The strength of the electrostatic force between two charged particles is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. The magnitude of the magnetic force on a wire is directly proportional to the number of charges coming through the wire (current), the strength of the magnetic field, and the length of the wire in that mag field. All change An electric field will be induced in an area where the magnetic field is changing with respect to time. The electric field is directly proportional to the rate of change of the magnetic field and is at right angle the changing magnetic field. A magnetic field will be induced in an area where the electric field is changing with respect to time. The magnetic field is directly proportional to the rate of change of the electric field and is at right angles changing electric field.

In the figure below, a rectangular loop of wire is in a region of space where there is a magnetic field that is everywhere directed into the page and decreasing. Which of the following is/are correct? Choose all that are correct. There will be a clockwise current created in the wire. The magnetic field is created by a clockwise current in the wire. There will be a counter-clockwise current created in the wire. The magnetic field is created by a counter-clockwise current in the wire. None of these is correct.

A long straight wire carrying a current of 2.61 A moves with a constant speed v to the right. A 5 turn circular coil of diameter 12.5 cm, and resistance of 3.25 un, lies stationary in the same plane as the straight wire. At some initial time the wire is to the left of the coil at a distance d = 6.00 cm from its center. 2.00 s later, the wire has moved to the right of the coil and is at a distance d from the center of the coil. What is the magnitude and direction of the induced current in the coil?

A magnetic field B is confined to a region ra and points out of the paper (the z- axis), r = 0 being the centre of the circular region. A charged ring (charge = q) of radius b(b> a) and mass m lies in the x-y plane with its centre at the origin. The ring is free to rotate and is at rest. The magnetic field is brought to zero in time T. The angular velocity w of the ring after the field vanishes is:

An ordinary gold wedding ring is tossed end over end into a running MRI machine with a 4.0 T field. The ring spends 1.1 s in the field, during which it completes 60 full rotations. If the ring has a resistance of 6.0 Ω and a diameter of 19 mm, what is the average power Pav dissipated by the ring?

A rectangular sheet of metal ABCD with side lengths AB = a, BC = a/2 and thickness t is kept with ABCD on the x-y plane. There is a uniform magnetic field B = Bk along the z direction. AB is along the x-axis. When the sheet is moved with speed v along the positive y direction, the resulting potential difference is ΔV₁. If the same sheet is moved with speed along the positive x direction, the resulting potential difference is ΔV₂. What is the value of the ratioΔV₁/ ΔV₂ ?

A single circular loop of wire is placed inside a long solenoid. The area vector of the loop is aligned with that of the solenoid. The area of the loop is A₁, and that of the solenoid is A₂. The solenoid has n turns per unit length. A current of I = I₀cos(ωt) flows in the solenoid. What is the equation for induced emf in the loop?

Two inductors: 1 mH and 100 μH are connected in series. How fast should the current change over time to produce a constant voltage of 33 mV across both of them (i.e. across the equivalent inductor).

The magnetic flux that passes through one tum of a 12-loop coil of wire changes to -40.0W, from 9.0W, in a time of 0.050s. The average induced current in the coil is 230A What is the resistance of the wire? Find the induced emf when the current in a 45.0mH inductor increases from zero to 515mA in 16.5ms.

A step-up transformer has 906 turns on its primary coil. If the input voltage is 94 V and the output Voltage is 150 V, how many turns are on the secondary coil? Round your answer to the nearest whole number. Do not add units.

Inductive charging is used to wirelessly charge electronic devices ranging from toothbrushes to cell phones. Suppose the base unit of an inductive charger produces a 1.20 x 10^-3 T magnetic field. Varying this magnetic field magnitude changes the flux through a 16.0-turn circular loop in the device, creating an emf that charges its battery. Suppose the loop area is 3.50 x 10^-4 m² and the induced emf has an average magnitude of 5.50 V. Calculate the time required (in s) for the magnetic field to decrease to zero from its maximum value.

A car with a 1.49 m long radio antenna travels at 104 km/h in a place where the Earth's magnetic field is 7.21 × 10−5 T. What is the maximum possible induced emf in the antenna as it moves through the Earth's magnetic field? 1.0.0031035 2. 0.000593619 3. 0.00124465 4. 0.0014541 5. 0.00131197 6. 0.000397335 7.0.00284149 8. 0.000565271 9. 0.000896327 10. 0.000539181 Answer in units of V.

In a step down transformer input voltage is 20000 volts and number of turns in primary are 4000. The supply voltage at which electricity is being distributed is 200 volts. Then number of turns in secondary required considering only 80% of flux linkage are 8x. Find x.

The charger cord used to recharge a cell phone contains a transformer that reduces 240 V AC to 5 V AC. For each 1,125 turns in the input coil, how many turns are there in the output coil? (Round your answer to at least one decimal place.)