Induced emf Definition and 245 Threads

Faraday's law says that an induced voltage across a conductor is directly proportional to the rate of change of magnetic flux through the conductor, but I am having trouble getting my head round how it works in this situation. Imagine a perfectly circular thin copper disc, and that this disc...

Suppose now i have connected a solenoid with a dc power supply of 10V When i increase the voltage to 20V the magnetic flux through the coil have increased will emf be induced shortly to oppose the change? what if i now change it to a 10V ac power supply so will there always be induced emf...

Homework Statement Determine the emf induced in the square loop in the figure if the loop stays at rest and the current in the straight wire is given by I(t) = (15.0 A)sin(2500t) where t is in seconds. The distance a is 12.0 cm, and b is 15.0 cm. Homework Equations In the question...

Homework Statement [PLAIN]http://img220.imageshack.us/img220/2589/44045733.png Semicircular wire MN of diameter L moves with speed v perpendicularly through a uniform magnetic field of strength B. 1. Find the magnitude of the induced emf generated between M and N. 2. State whether M...

Sometimes when i swipe my card at walmart it doesn't read it , And the guy was like let's put it a plastic bag and then try it, and it works and I've heard a couple of other people doing this. So when i slide my card the magnetic strip induces a voltage and reads the card. So why does...

Homework Statement A flat coil of wire consisting of 20 turns, each with an area of 50 cm^2 is positioned so that the normal to its plane is at the angle of 30 degrees to a uniform magnetic field that increases its magnitude at a constant rate from 2.0T to 8.0T in 2.0 s. Homework Equations...

Homework Statement A 25-turn circular loop of wire has a diameter of 1m. In 0.2 seconds it is flipped 180 degrees at a location where the magnitude of the Earth's magnetic field is 50 micro T. What is the emf generated in the loop?Homework Equations -(dB/dt)(A)=VThe Attempt at a Solution When I...

1. A 100-turn, 2.0-cm-diameter coil is at rest in a horizontal plane. A uniform magnetic field 60 degrees away from vertical increases from 0.50 T to 1.50 T in 0.60 s. 2. EMF = N*d(phi)/dt phi = flux = ABcos(theta) 3. dB/dt = 1/0.6 EMF = 1000*(1/0.6)*pi*r2*0.5 = 0.262 V Is...

Homework Statement A coil is wrapped with 247 turns of wire on the perimeter of a square frame of sides 27.3 cm. Each turn has the same area, equal to that of the frame, and the total resistance of the coil is 2.53. A uniform magnetic field is turnedon perpendicular to the plane of the coil...

ok, if i have a rectangular loop parallel to the screen and in a uniform constant magnetic field pointing perpendicularly outwards of the screen, if i move the loop to the right of the screen, will there be an induced emf in the loop? my understanding is that there will be? because we have a...

Homework Statement A coil with 253 turns of wire, a total resistance of 28 Ohms, and a cross-section area of 0.36m^2 is positioned in a plane perpendicular to the field of a powerful electromagnet. What average current is induced in the coil during the 0.33s that the magnetic field drops...

Ok... so there really isn't a homework problem that goes directly with what I am asking... I just want to understand how/why induction (magnet through a coil) gave certain results in our Science Workshop program... Here is what we did in our lab: We dropped a magnet (south end in first)...

Homework Statement The area of a 100 turn coil oriented with its plane perpendicular to a 0.28 T magnetic field is 4.3×10−2 m^2. Find the average induced emf in this coil if the magnetic field reverses its direction in 0.36 s. Homework Equations E = -N (flux - flux initial)/(t-to)...

Homework Statement The setup is a pair of two circular wires, a small one of radius b and a large one with radius 2b, both sharing the same center and located on the same plane. There is a magnetic field of strength B within the smaller circle that comes out of the paper towards the observer...

Homework Statement See picture for clarity. There are 2 infinite wires carrying a current i, one wire does it in the upward direction and the other wire in the downward direction. They are separated by a distance L+2d. Between them lies a circuit such that the part that moves with a velocity v...

-ve sign in expression of "induced emf" What is the concept behind putting negative sign in: e=[SIZE="2"]-[rate of change of flux] Which direction does it signify?? How does direction affect the equation? How and where can we use negative sign in other expressions of induced emf??

Homework Statement A 3 m long large coil with a radius of 15.7 cm and 130 turns surrounds a 7.2 m long solenoid with a radius of 5.7 cm and 4700 turns. The current in the solenoid changes as I=I_0 sin (2\pi f t) where I0= 30 A and f=60 Hz.Inside solenoid has 4700 turns and outside coil has...

Homework Statement A flat loop of wire of area 15.7 cm2 and 1.09 turns is perpendicular to a magnetic field whose magnitude decays in time according to B = 0.5 e−t/7. What is the maximum induced emf? Answer in units of V. Homework Equations \epsilon= \Delta\PhiB/\Deltat \epsilon=...

Homework Statement A solenoid of length 3.7 cm and diameter 0.95 cm is wound with 160 turns per cm. The current is decreasing at a rate of 38.0 A/s. (a) What is the induced emf in one of the windings? (b) What is the induced emf in the entire solenoid? Homework Equations emf =...

Homework Statement A circular coil with 35 turns of wire and a diameter of 19 cm is placed in a magnetic field given by B(t) = 6 t^2 + 6 t + 2 T where t is time in seconds. The field is perpendicular to the plane of the coil. What is the induced EMF at t = 5 s? Homework EquationsE=-d(magnetic...

Homework Statement A magnetic field is perpendicular to the plane of a single turn circular coil. The magnitude of the field is changing so that the emf of 0.80 V and a current of 3.2 A are induced in the coil. The wire is then re-formed into a single turn square coil, which is used in the...

[b]1. Derive an equation to find the induced EMF on an inner solenoid by a changing current on an outer solenoid. Homework Equations We're given the equation EoRMS=(No*Ai*(2*pi*f)*(permeability constant)*IiRMS)/Li for the induced EMF on the outer solenoid by a changing current in the...

Homework Statement A spacecraft is in a circular orbit of radius 3.1 X 10^4 km around a 1.9 X 10^30 kg pulsar. The magnetic field of the pulsar at that radial distance is 1.4 X 10^2 T directed perpendicular to the velocity of the spacecraft . The spacecraft is 0.20 km long with a radius...

Homework Statement A solid conductor travels at 150 m/s across a uniform .045T magnetic field. Which side is positively charged and what is the emf across this block? Homework Equations I actually solved for the emf no problem. I am having difficulty determining which side is...

What is the difference between an induced emf and a back emf? (i) i thought they were the same thing? . . .. .

Faraday's law says induced emf = - d(flux)/dt If this is applied to a loop where induced emf causes currents, and thus flux itself, do we have to consider that flux (of course we don't if it's constant)? If the external flux has a nonzero second derivative, then the induced emf is...

Two straight conducting rails form a right angle where their ends are joined. A conducting bar in contact with the rails starts at the vertex at time t = 0 and moves with a constant velocity of 7.00 m/s along them, as shown in Fig 31-44. A magnetic field with B = 0.350 T is directed out of the...

Homework Statement Homework Equations e=d/dt(BAN) The Attempt at a Solution

Homework Statement A 800-turn solenoid, 18 cm long, has a diameter of 2.9 cm. A 15-turn coil is wound tightly around the center of the solenoid. If the current in the solenoid increases uniformly from 0 to 3.1 A in 0.28 s, what will be the induced emf in the short coil during this time...

Homework Statement Resistance = R Radius = r Angle = theta B = 2cos(2t) Circular wire loop where magnetic field acts at theta degrees with respect to the normal of the wire loop. Find induced current and emf in wire loop. Find induced electric field at radial distance d from center of wire...

(As magnitudes) Faraday's law states that induced emf in a conducting loop by a changing flux, say x, is: emf = dx/dt Now if we have a circuit with the loop in series with wires (which are then tied together), how do I picture the voltages/currents in this circuit? I mean, the actual...

Homework Statement A 32 turn circular coil of radius 4.60 cm and resistance 1.00 is placed in a magnetic field directed perpendicular to the plane of the coil. The magnitude of the magnetic field varies in time according to the expression B = 0.0100t + 0.0400t2, where t is in seconds and B is...

A long, straight wire is in the same plane as a wooden, non-conducting loop. The wire carries an increasing current I in the direction shown in the figure (the current is pointing in the left direction). a. there will be no induced emf and no induced current b. there will be a...

Homework Statement A single coil with a radius of .02m is placed inside a 3m long solenoid that has 600 turns. The radius of the solenoid is 0.15m. The plane of the coil is perpendicular to the axis of the solenoid. The solenoid is connected to a battery, an ammeter and a switch. The ammeter...

Homework Statement Suppose you have a coil that is a certain distance from a magnet. Now you move the coil towards the magnet (until it is on top of the magnet) at a certain speed. Then you do the same thing only faster. Will the total induced emf be the same for both tries? Aka should the...

induced emf in secondary coil - help ASAP Please Homework Statement A very long, straight solenoid with a cross-sectional area of 6.00 cm2 is wound with 40.0 turns of wire per centimeter, and the windings carry a current of 0.250 A. A secondary winding of 2.00 turns encircles the solenoid...

An elastic conducting material is stretched into a horizontal circular loop of radius 20 cm and placed in a magnetic field of strength 0.5 T, directed vertically downwards. a. What is the magnetic flux through the loop? b. When released, the radius of the loop decreases at an initial rate...

Homework Statement A generator is constructed by rotating a coil of N turns in a magnetic field B at a frequency f. The internal resistance of the coil is R and the cross sectional area of the coil is A. Which of the following statements are true? (Give ALL correct answers, i.e., B, AC...

Homework Statement A circular coil, with radius of 10 cm, and 25 turns, rotates in a constant magnetic field of strength 2.4 T, with the axis of rotation perpendicular to the direction of the magnetic field. (a question about finding the induced voltage- 5.92 V) part C. If the...

Hello everyone :smile: I got a small question. In an electric motor when the coil rotates isn't this a change of magnetic flux. So wouldn't there be an induced emf in the coil? Any help would be appreciated. Thanks :smile:

Homework Statement A rectangular coil of 150 turns has dimensions of 23 x 70 cm and is located in a uniform 3 T magnetic field. In 1.2 s, the plane of the coil is rotated from a position where it makes an angle of 15° with the magnetic field to a position where it makes an angle of 72°...

Homework Statement http://img164.imageshack.us/img164/3313/qqqqo3.jpg Find the total magnetic flux through the coil at t=0 Given that the rate of change of flux at any time,t, is equal to 2 \pi f \phi sin 2 \pi ft, find the maximum instanteous value of the induced emf at any time & the...

Homework Statement An coil has 4000 turns of wire and a mean area of cross-section 25cm^2. A magnetic field of flux density 0.16T passes through it. When the magnetic field is reduced steadily to zero in 0.0050s, emf is induced across the terminals of the coil. Calculate the value of this...

Hello, I am currently working through Faraday's Law and I am confused when my two textbooks don't explain how they set the polarity of V_{emf}, particularly when they say "the sign convention for V_{emf} is arbitrary in that it depends on the assumed direction for dS". How is the polarity...

Homework Statement A circular loop of wire is rotated at constant angular speed around an axis whose direction can be varied. In a region where a uniform magnetic field points straight down, what must be the orientation of the loop's axis of rotation if the induced emf is to be zero...

A circular loop of wire has a changing magnetic field running through it...however, the magnetic field is not touching the wire; its contained so that it simply runs through the loop without touching the wire. Apparently, there is still an emf through the wire even though the magnetic field is...

A circular loop of wire has a changing magnetic field running through it...however, the magnetic field is not touching the wire; its contained so that it simply runs through the loop without touching the wire. Apparently, there is still an emf through the wire even though the magnetic field is...

Homework Statement a) If B (magnetic field) is perpendicular to the plane of a circular loop, then is it true that when B increases the induced emf is clockwise and when the B decreases the emf is counterclockwise? Or do you need to know whether it is pointing into/out of the page? Or would...

Homework Statement A radio antenna that receives an AM radio station that emits at 800 kHz is constituted of an inductor of 120 turns with a radius of 0.6cm. The inductor is home to an iduced emf du to a magnetic field oscillating from the radio wave. The magnetic field is...

[SOLVED] Induced emf: Faraday's Law and Lenz's Law Question The plane of a conductive loop with an area of 0.020 m^2 is perpendicular to a uniform magnetic field of 0.30 T. If the field drops to zero in 0.0045 s, what is the magnitude of the average emf induced in the loop...