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PRACTICE FINAL EXAM SOLUTIONS – IUPUI Physics 219
1) Consider the two point charges shown in the figure.
(A) Calculate the net electric field at x = 4.0 m.
Enet = 5.394 N/C
(B) Determine the direction of the net field.
θ = 233.13°
y
E1 = 8.99 N/C at 0°
3.0 m +20 nC
E2 = 7.192 N/C at –36.87°
E1
0
–16 nC
|
4.0 m
E2
x
2) A proton is accelerated from rest by a uniform electric field of magnitude 2.00×104 V/m. After the
proton travels 3.00 mm, calculate
(A) the potential difference through which it travels.
60 V
(B) the kinetic energy (in electron-volts) of the proton.
60 eV
(C) its final speed.
1.07 × 105 m/s
3) A copper of length 75 cm and diameter 2.5 mm has a potential difference of 9.0 V between its two
ends. The resistivity of copper is 1.70×10–8 Ω-m.
(A) What is its resistance?
2.6 × 10–3 Ω
(B) How much power is dissipated?
3.12 × 104 watts
(C) How many kilowatt-hours does it consume for an entire day? (31.2 kW)(24 hrs) = 749 kWh
2.0 Ω
4) In the circuit shown, the current through
the 2.0-Ω resistor is 1.5 A. Calculate
(A) the total equivalent resistance.
(B) the battery emf E.
3.0 Ω
6.0 Ω
4.0 Ω
E
(A) 1/Rp = (1/2.0) + (1/3.0) + (1/6.0)  Rp = 1.0 Ω so Req = Rp + 4.0 Ω = 5.0 Ω
(B) Voltage across 2.0-Ω resistor = IR = (1.5)(2.0) = 3.0 V
Voltage across all parallel resistors = 3.0 V so current thru Rp = ΔV/Rp = 3.0/1.0 = 3.0 A
1.0 Ω
Voltage across 4.0-Ω = IR = (3.0)(4.0) = 12 V
Total voltage E = 3.0 V + 12 V = 15 V
4.0 Ω
5) A straight wire 50 cm long has a current of 4.0 A directed upward (↑). The wire experiences a force
of 0.01 N to the right (→) due to a perpendicular magnetic field. Determine
(A) the magnitude of the magnetic field.
0.005 T
(B) the direction of the magnetic field.
out of page, 
6) A square loop of wire of side 40 cm is exposed to a magnetic field perpendicular to its area. The
field decays at a rate of 10 T/s. Calculate the induced emf.
–1.6 V
7) With a magnifying glass, a kid views an insect of height 0.92 cm. She sees the insect magnified 3.5
times when the glass is held 3.0 cm from it. Calculate
(A) the focal length of the lens.
+2.33 cm
(B) the height of the image.
–3.22 cm
8) A diffraction grating is designed to have the 2nd order maxima at 10° from the central maximum for
red light (λ = 700 nm). How many lines per cm does the grating have?
1240 lines/cm
9) The proper lifetime of a muon is 2.20 μs. While in motion, the muon’s lifetime is measured to be
4.60 μs. Calculate the muon’s speed as a fraction of the speed of light. Carry your answer out to the
thousandths’ place.
0.878
10) Light of wavelength 340 nm is incident upon a metal surface and ejects electrons with a maximum
speed of 3.5×105 m/s. Calculate the work function of the metal in electron-volts.
Kmax = ½ mvm2 = 5.58 × 10–20 J = 0.349 eV
hf = hc / λ = 5.85 × 10–19 J = 3.656 eV
φ0 = hf – Kmax = 3.307 eV
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