online final exam spring part a-problems

phalo (gdp423) – Online Final Exam Spring Part A – krieger – (201212) 1

This print-out should have 30 questions.Multiple-choice questions may continue onthe next column or page – find all choicesbefore answering.

001 10.0 pointsA coil is wrapped with 774 turns of wire onthe perimeter of a circular frame (of radius61 cm). Each turn has the same area, equalto that of the frame. A uniform magneticfield is directed perpendicular to the plane ofthe coil. This field changes at a constant ratefrom 27 mT to 41 mT in 77 ms.What is the magnitude of the induced E in

the coil at the instant the magnetic field hasa magnitude of 40 mT?Answer in units of V

002 10.0 pointsIf 4.2× 1021 electrons pass through a 30 Ωresistor in 12 min, what is the potential dif-ference across the resistor? The elementarycharge is 1.602× 10−19 C .Answer in units of V

003 (part 1 of 2) 10.0 pointsThe second-order bright fringe (m = 2) is4.6 cm from the center line.

4.6

cm

1.08 m

0.0287mm

S1

S2

θ

viewing

screen

Determine the wavelength of the light.Answer in units of nm

004 (part 2 of 2) 10.0 pointsCalculate the distance between adjacentbright fringes.Answer in units of cm

005 10.0 pointsAn electron transfers across a potential differ-ence of 6.5× 105 V.

What energy must it be given to accomplishthis?Answer in units of J

006 (part 1 of 4) 10.0 pointsA convex lens forms a real image 4 timesthe size of the object. The distance betweenobject and image is 37 cm.Find the focal length of the lens.Answer in units of cm

007 (part 2 of 4) 10.0 pointsA concave lens forms a virtual image 0.7 timesthe size of the object. The distance betweenobject and image is 6.6 cm.Find the focal length of the lens.Answer in units of cm

008 (part 3 of 4) 10.0 pointsA convex lens forms a virtual image 5 timesthe size of the object. The distance betweenobject and image is 5.8 cm.Find the focal length of the lens.Answer in units of cm

009 (part 4 of 4) 10.0 pointsA convex lens forms a real image 0.6 timesthe size of the object. The distance betweenobject and image is 30 cm.Find the focal length of the lens.Answer in units of cm

010 10.0 pointsAn infinitely long straight wire carrying acurrent I1 = 23.2 A is partially surroundedby a loop as in figure. The loop has a lengthL = 52.7 cm, a radius R = 9.83 cm, andcarries a current I2 = 29.4 A. The axis of theloop coincides with the wire.


R

L I1

I 2

Calculate the force exerted on the loop.Answer in units of µN

011 10.0 pointsA convex lens forms a real image 3 timesthe size of the object. The distance betweenobject and image is 32 cm.Find the focal length of the lens.Answer in units of cm

012 10.0 pointsA 30.5 turn circular loop of wire has a diame-ter of 0.524 m. The plane of the circular loopmakes and angle of 150 to the Earth’s mag-netic field. In 0.124 s the coil is flipped at alocation where the magnitude of the Earth’smagnetic field is 67 µT.What is the magnitude of the average emf

generated in the loop?Answer in units of µV

013 10.0 pointsA 58.6 turns circular coil with radius 2.8 cmand resistance 9.11 Ω is placed in a magneticfield directed perpendicular to the plane ofthe coil. The magnitude of the magnetic fieldvaries in time according to the expression

B = a1 t+ a2 t2 ,

where a1 = 0.0245 T/s, a2 = 0.0132 T/s2 areconstants, time t is in seconds and field B isin Tesla.Find the magnitude of the induced emf in

the coil at t = 2.55 s.Answer in units of V

014 (part 1 of 4) 10.0 points

An air-filled capacitor consists of two parallelplates, each with an area of 9.63 cm2, sepa-rated by a distance of 0.74 mm. A(n) 16 Vpotential difference is applied to these plates.The permittivity of a vacuum is 8.85419×

10−12 C2/N ·m2.Find the magnitude of the electric field be-

tween the plates.Answer in units of V/m

015 (part 2 of 4) 10.0 pointsFind the magnitude of the surface charge den-sity.Answer in units of C/m2

016 (part 3 of 4) 10.0 pointsFind the capacitance.Answer in units of F

017 (part 4 of 4) 10.0 pointsFind the magnitude of the charge on eachplate.Answer in units of pC

018 10.0 pointsAn airplane is flying through a thundercloudat a height of 1850 m. (A very dangerousthing to do because of updrafts, turbulence,and the possibility of electric discharge.)If there is a charge concentration of 47.5 C

at height 4460mwithin the cloud and−24.2 Cat height 720 m, what is the magnitude of theelectric field E at the aircraft? The Coulombconstant is 8.98755× 109 N ·m2/C2.Answer in units of V/m

019 (part 1 of 2) 10.0 pointsCalculate the speed of a proton that is acceler-ated from rest through a potential differenceof 112 V.Answer in units of m/s

020 (part 2 of 2) 10.0 pointsCalculate the speed of an electron that isaccelerated through the same potential differ-ence.Answer in units of m/s


021 (part 1 of 2) 10.0 pointsAn electric motor has 119 turns of wirewrapped on a rectangular coil, of dimensions3.48 cm by 3.26 cm. Assume that the mo-tor uses 15 A of current and that a uniform1.16 T magnetic field exists within the motor.What is the maximum torque delivered by

the motor?Answer in units of Nm

022 (part 2 of 2) 10.0 pointsIf the motor rotates at 1770 rev/min, what isthe peak power produced by the motor?Answer in units of W

023 10.0 pointsIn a hydroelectric installation, a turbine de-livers 1730 hp to a generator, which in turnconverts 67.4% of the mechanical energy intoelectrical energy.Under these conditions, what current will

the generator deliver at a terminal potentialdifference of 1280 V?Answer in units of A

024 10.0 pointsA small electrically charged object is sus-pended by a thread between the verticalplates of a parallel-plate capacitor.

A B

~E

+ −

E

256 mg

18 nC

θθ=21

6.3 cm

What is the potential difference betweenthe plates? The acceleration of gravity is9.8 m/s2 .Answer in units of kV

025 10.0 pointsTwo long, parallel wires, each having a massper unit length of 56.6 g/m, are supported ina horizontal plane by strings 2.9 cm long, as inthe figure. Each wire carries the same currentI, causing the wires to repel each other sothat the angle between the supporting stringsis 15.77.The acceleration due to gravity is 9.8 m/s2

and the permeability of free space is 1.25664×10−6 T ·m/A.

y

xz

a θ

Find the magnitude of each current.Answer in units of A

026 10.0 pointsA flint glass plate (index of refraction of 1.08)rests on the bottom of an aquarium tank. Theplate is 5.04 cm thick (vertical dimension)and covered with water (index of refraction of1.19) to a depth of 12.3 cm.Calculate the apparent thickness of the

plate as viewed from above the water. (As-sume nearly normal incidence.)Answer in units of cm

027 10.0 pointsLight of wavelength 546 nm from a mercuryarc falls on a diffraction grating ruled with38400 lines/in.What is the angular separation between the

first-order images on either side of the centralmaximum? (Caution: do not use small angleapproximation here.)Answer in units of

028 10.0 pointsPenny wishes to take a picture of her image ina plane mirror.


If the camera is 2.1 m in front of the mirror,at what distance should the camera lens befocused?Answer in units of m

029 10.0 pointsA 18 Ω metal wire is cut into three equalpieces that are then connected side by side toform a new wire the length of which is equalto one-third the original length.What is the resistance of this new wire?Answer in units of Ω

030 10.0 pointsThe average kinetic energy of gas atoms corre-spond to the energy difference ∆E = 10.2 eVbetween the ground state and the first excitedstate of hydrogen.What would the temperature of H gas

have to be? The value of the Boltzmannconstant is 1.38× 10−23 J/K and 1 eV =1.6× 10−19 J/eV .Answer in units of K

online final exam spring part a-problems

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