PhysicsII
Sheet#5
Samer Zyoud
Problem1:
A wire made from aluminum (resistivity 2.8 10 8 m ) has a square cross section of side 2
mm. Determine the current in the wire if the electric field in it is 0.014 N/C.
Problem2:
A 2.0-m long silicon wire which has a rectangular cross section with width w = 3.2 cm and height
h = 2.5 cm carries a current I = 0.5A when 1.1 V is applied across its length. If the number
of free charges per unit volume is 1.5x1023 m3,
a)
b)
c)
d)
What is the current density J?
What is the drift velocity vd?
What is the magnitude of the electric field applied to the wire?
What is the conductivity of the silicon?
Problem3:
The electron density in copper is 8.49 X 1028 electrons/m3. The electron charge is e = -1.6 X 10-19 C.
Find the electron drift velocity when a 1.00 A current is present in a copper wire with a 0.4 cm2
cross-section.
Problem4:
A small bulb is rated at 7.5 W when operated at 125 V. The tungsten filament has a temperature
coefficient f resitivity α = 4.5 X 10-3 / oC. When the filament is hot and glowing, its temperature is
seven times the room temperature (20 oC). What is the resistance of the filament (in ohms) at room
temperature?
Problem5:
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PhysicsII
Sheet#5
Samer Zyoud
Problem6:
A wire made from aluminum (resistivity 2.8 10 8 m ) has a square cross section of side 2
mm. Determine the current in the wire if the electric field in it is 0.014 N/C.
Problem7:
Problem8:
A 10-m length of aluminum wire has a diameter of 1.5 mm. It carries a current of 12 A. If the density of
aluminum is 2.7 kg/m3 , the molecular mass M = 26.98 x 10-3 kg/mol, and the resistively ρ = 2.8 x 10–8
Ω.m. Assuming that each Al atom contributes with one free electron. Find (a) The current density. (b)
The drift velocity (c) The electric field in the wire.
Problem9:
Problem10:
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PhysicsII
Problem11:
Problem12:
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Sheet#5
Samer Zyoud
Physics II
Sheet#6
Problem 1
Problem 2
Problem 3
What is the current in the 10-Ω resistor shown in the figure?
+
Ω
−
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Ω
Ω
Samer Zyoud
Physics II
Sheet#6
Samer Zyoud
Problem 4
In the figure, if Є1 = 4.0 V, Є2 = 12.0 V, R1 = 4 Ω, R2 = 12 Ω, C = 3 µF, Q = 18 µC, and I = 2.5 A, what is
the potential difference Va – Vb?
+
−
+
ε
ε
−
−−
++
Problem 5
In an RC circuit, how many time-constants must elapse if an initially
uncharged capacitor is to reach 80% of its final potential difference?
Problem 6
In the figure , suppose the switch has been closed for a time sufficiently long for the
capacitor to become fully charged. Find (a) the steady-state current in each resistor and
(b) the charge Q on the capacitor and (c) find the time interval required for the charge on
the capacitor to fall to one-fifth its initial value.
Problem 7
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Physics II
Sheet#6
The ammeter shown in the Figure reads 2.00 A. Find I1, I2, and
1.
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Samer Zyoud
ε.
Physics II
Sheet#6
Problem 8
In the circuit I = 0.2 A and = 18 V. Determine
a) The current in each resistor.
b) The value of R.
c) The power dissipated in the resistor labeled by 4R.
Problem 9
In the circuit I = 0.5 A and R = 12 . Determine
a) The current in each resistor.
b) The emf .
c) The power dissipated in the resistor labeled by R.
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Samer Zyoud
PhysicsII
Problem1:
Problem2:
Problem3:
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Sheet#7&8
Samer Zyoud
PhysicsII
Sheet#7&8
Samer Zyoud
Problem4:
A magnetic field has a magnitude of 1.2x10-3 T, and an electric field has a magnitude of 4.6x103 N/C.
Both fields point in the same direction. A positive 1.8 µC charge moves at a speed of 3.1x106 m/s in a
direction that is perpendicular to both fields. Determine the magnitude of the net force that acts on the
charge.
Problem5:
A coil of wire has an area of 2x10-4 m 2 , consists of 100 loops or turns, and contains a current of 0.045
A. The coil is placed in a uniform magnetic field of magnitude 0.15 T. (a) Determine the magnetic
moment of the coil. (b) Find the maximum torque that the magnetic field can exert on the coil.
Problem6:
A circular area with a radius of 6.5 cm lies in the xy-plane. What is the magnitude of the magnetic flux
through this circle due to a uniform magnetic field B=0.23 T, that lies in the (a) +z direction, (b) at an
angle of 53.1o from the +z direction, (c) in the +y direction.
Problem7:
Problem8:
Problem9:
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PhysicsII
Sheet#7&8
Samer Zyoud
Problem10:
Problem11:
A circular loop of radius R carries a current I2 in a clockwise direction as shown. The center of the loop is
at a distance D =2R above a long straight wire.
a) Derive an expression for the net magnetic field at the center of the loop in terms of o, I1, I2 and
R
b) What are the magnitude and direction of the current I1 in the wire if the magnetic field at the
center is zero?
Problem12:
The conducting rod ab shown in the figure makes contact with metal rail ca and db. The apparatus is in a
uniform magnetic field of 0.80 T, perpendicular to the plane of the figure.
a) Find the magnitude of the emf induced in the rod when it is moving to the right with a speed
of 7.5 m/s.
b) In what direction does the current flow in the rod?
c) If the resistance of the circuit abdc is 1.5 , find magnitude and direction of the force required
to keep the rod moving to the right with a constant speed of 7.5 m/s.
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PhysicsII
Problem13:
Problem14:
Problem15:
Problem16:
Problem17:
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Sheet#7&8
Samer Zyoud
PhysicsII
Problem18:
Problem19:
Problem20:
Problem21:
Problem22:
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Sheet#7&8
Samer Zyoud
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