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This is the Past Paper of General Physics which includes Unit of Electrical Resistance, Average Rate, Electron's Progress, Current Through Resistor, Voltage Across Particular Resistor, Dissipated Power etc. Key important points are: Step Down Transformers, Power-Line Distribution Voltage, Charged Particle, Speed of Particle, Resistor and Capacitor, Inductor Value, Wavelength of Waves, Impedance of Tuning Circuit
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TOUGALOO COLLEGE
PHY 124, Introduction to Physics II
Exam 3
4/10/
The exam consists of 5 questions. There will be 90 minutes to complete the exam. Allowable resources
are the provided equation sheet(s) and your calculator. The questions may not be worth the same
number of points, read the entire exam before beginning work. Put your name on all pages.
Problem 1 25
Problem 2 25
Problem 3 20
Problem 4 20
Problem 5 10
Total 100
a) (5 pts) Transformers are often used in AC circuits to change one voltage to another, such as the
step-down transformers that the power company uses to convert the power-line distribution voltage to
voltages usable inside a house. Why are transformers not used in this fashion in DC circuits?
b) (5 pts) If you cut a bar magnet in half, will you end up with only a North Pole in one hand and only
a South Pole in the other hand? (Why or why not?)
c) (5 pts) The force on a charged particle due to motion in a magnetic field can not change the speed of
the particle. Why is this so? (And what does it change?)
d) (5 pts) Given an AC circuit with a resistor and capacitor, would you make the capacitor value larger
or smaller to allow more current to flow? (And why?)
e) (5 pts) Given an AC circuit with a resistor and an inductor, would you make the inductor value
larger or smaller to allow more current to flow? (And why?)
of hollow PCV pipe with an outside diameter of 3 cm.
a) (5 pts) What is the inductance of the solenoid?
b) (5 pts) The inductor is connected in series with a 10 resistor, a 12 V battery, and a switch. How
much energy will be stored in the magnetic field produced by the inductor when the current has been
on for a long time?
c) (5 pts) How long will it take the current through this inductor to reach 63% of the maximum value
after the switch is first closed?
d) (5 pts) Draw a sketch of the solenoid clearly showing the direction of the current flow through the
solenoid and the magnetic field resulting from this current flow.
a) (5 pts) Calculate the magnitude of the magnetic field at a distance of 0.5 m from the wire.
b) (5 pts) Make a sketch of the wire indicating direction of current flow and the magnetic field lines in
the region of space near the wire.
c) (5 pts) If this wire is in an external magnetic field of 0.3 T and the current flow direction makes a 30
degree angle with this field, calculate the magnitude of the force exerted on the wire.
d) (5 pts) Indicate the direction of the magnetic force on this wire in the diagram below. (Note: The
magnetic field shown here is the external field, not the field created by the current in the wire itself!)
I
B
θ=
o
(5 pts) Extra Credit:
A coil is being designed to provide power-failure backup for a computer system. The computer draws
200 W (at 120V) and will require power for 10 seconds in order to shut down properly. What inductance
will be required to satisfy this need?
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