PHY2049C - Hong Final Review
A long straight wire si parallel to one edge and is in the plane of a single-turn rectangular loop as shown. If the current is increasing at a rate of c, what is the direction and magnitude of the emf induced in the loop?
Out of the page
What is the resonant frequency [in Hz] for a series RLC circuit where R = 10 ohms, C = 5.00 micro F, and L = 2.00 mH? Express your answer using at least three sig. figures.
1590 Hz
The magnetic flux through a metal ring varies with time t according to at^3 - bt^2, where b is in webers, a = 6.00 Wb s^-3, b = 18.0 Wb s^-2, and t is in seconds. The resistance of the ring is 3.10. For the interval from t=0 to t=2.00 s, determine the maximum current induced in the ring.
5.81 A
The flexible loop in the figure below has a radius of 14.0 cm and is in a magnetic field of magnitude 0.140 T. The loop is grasped at points A and B and stretched until its area is nearly zero. If it takes 0.170 s to close the loop, what is the magnitude of the average induced emf in it during this time interval?
50.7 mV
A solenoid of radius R = 3.70 cm has N=560 turns and a length of d=25.0 cm. Find its inductance L and the rate dI/dt at which current must change through it to produce an emf of 60.0 mv.
6.78 mH and 8.85 A/s
A circular loop of wire of resistance R = 0.5 ohm and radius r = 7.80 cm is in a uniform magnetic field directed out of the page as in the figure below. A clockwise current of I = 2.60 mA is induced in the loop. Find the rate at which the field is changing with time.
68 mT/s
The current in a 70.0-mH inductor changes with time i = 4.00t^2 0 7.00t, where i is in amperes and t is in seconds. Find the magnitude of the induced emf at t=1.00s
70 mV
A circular loop of wire is falling toward a wire carrying a current to the left. What is the direction of the induced current in the loop of wire?
Counterclockwise
Two coils, held in fixed positions, have a mutual inductance of 170 uH. What is the peak emf in one coil when the current in the other coil is i(t) = 13.0 sin(1.25x10^3t), where i is in amperes and t is in seconds?
2.76 V
A conducting bar of length l moves to the right on two frictionless rails as shown in the figure below. A uniform magnetic field directed into the page has a magnitude of 0.290 T. Assume R = 9.10 ohm and l = 0.390 m. If the bar moves at 0.668 m/s, what is the magnitude and direction of the induced current in the resistor?
8.30 mA, counterclockwise
A 35-turn circular coil of radius 4.6 cm and resistance 1.00 ohm 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 = 0.010t + 0.040 t^2, where B is in tesla and t is in seconds. Calculate the induced current in the coil at t = 4.6 s.
87.9 mA
The eye is most sensitive to light having a frequency of 5.45 x 10^14 Hz, which is in the green-yellow region of the visible electromagnetic spectrum. What is the wavelength of this light?
5.50e-07 m
Which of the following best describe the voltage-current phase-relationship shown in the curve?
I is higher than E, both going up and right
Which of the following represents more capacitive load ie, XC > XL?
Imax > Vmax
In the figure current I is decreasing. What is the direction of induced current?
to the right
What is the maximum amplitude of an AC source if the AC source has an rms value of 120 volts?
169.7 V
What is the impedance [in ohm] for the circuit?
1800 ohms
A convex mirror has a focal length of -0.2 m. What is the position of the resulting image (in m) if the image is upright and four times smaller than the object?
-0.15m
A coil is wrapped with 100 turns of wire on the perimeter of a square frame (side length = 20 cm). Each turn has the same area as the frame. A uniform magnetic field perpendicular to the plane of the coil changes in magnitude at a constant rate from 0.50 T to 0.90 T in 4.0s. What is the magnitude of the induced emf in the coil while the field is changing?
0.4 V
A flat loop wire consisting of a single turn of cross-sectional area 8.20 cm is perpendicular to a magnetic field that increases uniformly in magnitude from 0.5 T to 3.30 T in 1.03 s. What is the resulting induced current if the loop has a resistance of 2.40 Omega?
0.929 mA
Consider the circuit in the figure below, taking E = 6.00 V, L=8.20mH, and R = 8.20 ohm. What is the inductive time constant of the circuit? What is the value of the final steady-state current?
1 ms. 0.732 A
An aluminum ring of radius r1 = 5.00 cm and a resistance of 3.20 x 10^-4 ohm is placed around one end of a long air-core solenoid with 1025 turns per meter and radius r2 = 3.00 cm. Assume the axial component of the field produced by the solenoid is one-half as strong over the area of the end of the solenoid as at the center of the solenoid. Also assume the solenoid produces negligible field outside its cross-sectional area. The current in the solenoid is increasing at a rate of 270 A/s. What is the magnitude and direction of the induced current in the ring?
1.536 A, Counterclockwise
A conducting bar moves as shown near a long wire carrying a constant current 30 A. If a = 8mm, L = 20 cm, and v = 11 m/s, what is the induced emf on the bar?
1.65 mV
A conducting rod (length = 89 cm) rotates at a constant angular rate of 15 revolutions per second about a pivot at one end. A uniform field (B = 60mT) is directed perpendicularly to the plane of rotation. What is the magnited of the emf [in volts] induced between the ends of the rod? Express your answer using at least 2 significant figures.
1.8 V
What is the direction of the induced current in teh resistor R when the bar magnet is moved to the left?
a to b
Which of the following phasors best represents current i(t) = 2*sin(Pi*t) at t=1.8 s?
Down and left
In the circuit diagrammed below, take E = 10.0 V and R = 23.5 ohm. Assume the switch is open for T < 0 and is closed at t = 0. On a single set of axes sketch graphs of the current in the circuit as a function of time for t> 0, assuming the following.
Inductance small (0.24 H): sharp rise and flatten at 0.4 Inductance intermediate(2.4 H): Steady increase before leveling off around 0.5 s Inductance very large (24 H): Curve upward towards 0.4
The frequency of the AC source is adjusted while its voltage amplitude is held constant. When does the light bulb glow the brightest?
It glows brightest at high frequencies.
The frequency of the AC source is adjusted while its voltage amplitude is held constant. When does the light bulb glow the brightest?
It glows brightest at low frequencies.
A circular loop of wire is held in a uniform magnetic field, with the plane of the loop perpendicular to the field lines. Which of the following will not cause a current to be induced in the loop?
Keeping the orientation of the loop fixed and moving it along the field lines.
Consider an electromagnetic wave traveling in the positive y direction. The magnetic field associated with the wave at some location at some instant points in the negative x direction as shown in the figure below. What is the direction of the electric field at this position and at this instant?
The negative z direction
As in question 15 above, current I is decreasing. (The coil has no resistance.) Which of the induced potentials is higher Va or Vb? Hint. Treat the solenoid as a battery and then consider the direction of current in the "entire" loop of circuit due to the induced emf.
Vb
In SI units, the electric field in an electromagnetic wave is described by Ey = 120 sin(1.40 x 10^7 - wt) a) find the amplitude of the corresponding magnetic field oscilations b) find the wavelength c) Find the frequency
a) 0.4 uT b) 0.449 um c) 6.88e+14 Hz
Consider a RL circuit, taking E = 6.00 V, L - 8.20 mH, and R = 8.20 ohm a) What is the inductive time constant of the circuit? b) What is the value of the final steady-state current?
a) 1 ms b) 0.732 A
An inductor (L = 410 mH), a capacitor (C = 4.43 uF), and a resistor (R = 450 ohm) are connected in series. A 50.0-Hz AC source produces a peak current of 250 mA in the circuit. a) Calculate the required peak voltage b) Determine the phase angle by which the current leads or lags the applied voltage
a) 185 V b) 52.7 and current leads
The LC circuit of a radar transmitter oscillates at 16.6 GHz a) What inductance is required for the circuit to resonate at this frequency if its capacitance is 4.80 pF? b) What is the inductive reactance of the circuit at this frequency?
a) 19.2 pH b) 2 ohm
An RLC circuit consists of a 160 ohm resistor, a 21.0 uF capacitor, and a 520 mH inductor, connected in series with a 120 V, 60.0 Hz power supply. a) What is the phase angle between the current and applied voltage? b) Which reaches its maximum earlier, the current of the voltage?
a) 23.5 degrees b) voltage
Consider a series RLC circuit having the parameters R = 425 ohm, L = 1.25 H, and C = 3.5 uF. The applied voltage has an amplitude of 150.0 V and a frequency of 60.0 Hz. a) calculate angular frequency w b) Calculate Xc, Xl, and Z c) What is the phase angle between the current and the applied voltage? Which of voltage and current leads? d) Is this circuit more inductive or more capacitive? e) Find the maximum current and voltage across each element? f) What is the power factor? What is the resonance frequency (in Hz)? h) For a maximum power supply to the load R, how much change do you have to make for C or L or w?
a) 377 rad/s b) Xc = 758 ohm, Xl = 471 ohm, Z = 513 ohm c) -34 degrees. Current leads by 34 degrees. d) more capacitive e) Im = 0.293 A, Vc = 222 V; Vl = 138 V; Vr = 124 V f) 0.829 g) 76 Hz h) w = +101 rad/s; l = +0.75 H; c = +2.1 uF
A series RLC circuit has components with the following values: L = 16.0 mH, C = 88.0 nF, R = 30.0 ohm, and Vmax = 100V, with v = Vmax sin omega*t a) Find the resonance frequency of the circuit b) Find the amplitude of the current at the resonance frequency c) Find the amplitude of the voltage across the inductor at resonance
a) 4.24. kHz b) 3.33 A c) 1.42 kV
The wavelength of red helium-neon laser light in air is 632.8 nm a) what is its frequency? b) What is its wavelength in glass that has an index of refraction of 1.48? C) What is its speed in teh glass?
a) 4.74e+14 Hz b) 428 nm c) 203 Mm/s
The figure shows a refracted light beam in linseed oil making an angle of 28.2 with the nromal line NN'. The index of refraction of linseed oil is 1.48 a) Determine the angle theta b) Determine the angle theta prime
a) 44.4 b) 31.6
The index of refraction for red light in water is 1.331 and that for blue light is 1.340. A ray of white light enters the water at an angle of incidence of 82.4 degrees. a) What is the underwater angle of refraction for the red component of the light? b) What is the underwater angle of refraction for the blue component of the light?
a) 48.1 degrees b) 47.8 degrees
An AC voltage of the form v = 75 sin 290t where v is in volts and t is in seconds, is applied to a series RLC circuit. If R = 42.0 ohm, C = 30.0 uF, and L = 0.250 H, find the following. a) the impedance of the circuit b) the rms current in the circuit c) the average power delivered to the circuit
a) 59.7 ohm b) 0.888 A c) 33.1 W
An object located 30.0 cm in front of a lens forms an image on a screen 8.00 cm behind the lens a) Find the focal length of the lens b) Determine the magnification c) Is the lens converging or diverging?
a) 6.32 cm b) -0.267 c) converging
The figure below shows a plane electromagnetic sinusoidal wave propagating in the x direction. Suppose the wavelength is 42.0 m and the electric field vibrates in teh xy plane with an amplitude of 24.0 V/m. a) Calculate the frequency of the wave b) Calculate the magnetic field B when the electric field has its maximum value in the negative y direction
a) 7.14 MHz b) Magnitude 80 nT, direction -z
Consider a series AC circuit contains a resistor, an inductor of 250 mH, a capacitor of 4.00 uF, and a source with V max = 240 V operating at 50 Hz. The maximum current in the circuit is 180 mA. a) Calculate the inductive reactance. b) calculate the capacitive reactance c) calculate the impedance d) calculate the resistance in the circuit e) calculate the phase angle between the current the source voltage
a) 78.5 ohm b) 796 ohm c) 1.33 kilo-ohm d) 1.12 kilo-ohm e) -32.5 degree
An object is located 24.0 cm to the left of a diverging lens having focal length f= -38.0 cm. a) determine the location of the image. b) Determine the magnification of the image c) construct a ray diagram for this arrangement
a) Distance 14.7 cm, location: to the left of the lens b) 0.613 c) picture
An object of height 10 cm is placed 6.1 cm in front of a spherical mirror. a) Find the image distance q and the magnification if the mirror is concave with focal length 5 cm b) Find the image distance q and magnification if the mirror is convex with focal length 5 cm
a) q=27.7 Cm, M = 4.55 b) q= -2.75 Cm, M = 0.45