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DC Circuits
1.) An emf source of 6.0V is connected to a purely resistive lamp and a current of 2.0 amperes flows. All the wires
are resistance-free. Draw the ckt diagram. What is the resistance of the lamp?
2.)The current flowing in a circuit containing four resistors connected in series is I = 1.0 A. The potential
drops across the first, second and third resistors are, respectively: V = 5V, V = 8V andV = 7V . The equivalent
resistance of the circuit is R = 30. Ohm. Draw the ckt diagram. Find the total voltage supplied by the battery, and
also current, voltage drop, and resistance of each resistor in the circuit.
3.)In the following ckt find the total current I. The current in, and voltage across in the resistors R1, R2 and
R3 and the power dissipated in each resistor.
FIG. 1: Resistance in parallel
4.)In the following ckt find the total current I. The current in, and voltage across in the resistors R1, R2, R3, R4
and R5 and the power dissipated in each resistor. The EMF in the ckt is 6.7V.
FIG. 2: Combination series and parallel resistance.
5.)In the following ckt find the equivalent resistance across point AB.
FIG. 3: Combination series and parallel resistance.
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6.)A DC circuit is made up of an 25.0 V battery and four resistors as shown.
(A) Before the switch is closed what is the current flow produced by the battery and through each resistor?
(B) After the switch is closed what is the current flow produced by the battery and the current through each resistors?
(C) What is the potential difference between points a and b both before and after the switch is closed?
(D) After the switch is closed what is the current flow through the middle branch containing the switch? Which
direction does the current flow, from a to b or from b to a?
7.) A parallel plate capacitor has an area of 5.00cm2 and a capacitance of 3.50 pF. The capacitor is connected to
a 12.0 V battery. After the capacitor is completely charge up, the battery is removed.
(A) What must be the separation of the plates and the charge density on the plates?
(B) What is the magnitude of the electric field between the plates, and how much energy is stored in the electric
field between the plates?
8.)Three capacitors are connected to a battery of unknown voltage as shown in the circuit diagram?
voltage drop across the first capacitor C1 is 11.0 V.
(A) What is the effective capacitance of the three capacitors?
(B) What is voltage of the battery?
(C) Which capacitor has the larges charge stored in it?
(D) How much work did it take the battery to charge up all the capacitors?
The
8.) A 100 mF capacitor is connected in series with a 10.0 W resistor. This combination is connected in parallel
with a 25.0 W resistor. Both branches are then connected in parallel to a 4.50 V battery that can be switched on
and off. The capacitor starts off fully discharged.
(A) What is the time constant in both branches when the switch is closed?
(B) What is the maximum charge that the capacitor can attain after the switch is closed?
(C) When will the voltage drop across the 10.0 W resistor be equal to 1.50 V after the switch is closed?
(D) If the switched is opened, what will be the value of the new time constant and in which direction will the current
flow through the 10.0 W resistor?
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(E) If the switch is opened after the capacitor is fully charged, how long will it take for there to be only one electron
on the capacitor?
(F) If the switch is opened after the capacitor is fully charged, how long will it take for the voltage across the 25.0
W resistor to drop to 1.50 V?
9.)Two point charges q1 = −88.0 nC & q2 = 360 nC are located at the fixed positions at x1 = 22.0 cm and
x2 = 96.0 cm on the x-axis.
(A) What is the electric potential due to both charges at x = 50.0 cm?
(B) Where on the x-axis is the electric potential due to both charges equal to zero?
(C) How much work is required to move a third charge q3 = 13.0 mC from the origin to x = 50.0 cm along any path
(that does not go through one of the charges)?
(D) If a fourth charge q4 with a charge of -11.0 mC and a mass of 3.90 gm is released from rest at the origin, what is
the charge’s final speed and direction when it is very far away from the other two charges?
10.)A positive and a negative charge of the same magnitude are placed equal distances from the origin on
the x-axis. The negative charge -q is place a distance a to the right of the origin, and the positive charge +q is placed
a distance a to the left of the origin.
(A) Determine the symbolic expression for both the magnitude and direction of the electric field at any point y on
the y-axis as a function location of the charges and their magnitude.
(B) If a = 11.0 cm and q = 1.70 mC, what is the size of the electric field at a distance of 3.80 mm above the origin
on the y-axis?
(C) At what distance from the origin on the y-axis will the electric field created by the two charges have a magnitude
of 7.30x10 3 N/C?
(D) What is the magnitude and direction of the force on a third charge of magnitude -86.0 mC placed 3.80 mm above
the origin on the y-axis?