Physics 110 Problems - My Solutions
Dr. Hulan E. Jack Jr.
Chapter13 Q13
Griffith, W. Thomas; The physics of everyday phenomena: a conceptual introduction for
physics;4th Edition ISBN 0-07-250977-5
THE PROBLEM STATEMENT
Ch13 Q13 Two resistors are connected in series with a battery as shown in the diagram. R1, is
less than R2.
a. Which of the two resistors, if either, has the greater current flowing through it? Explain.
b. Which of the two resistors, if either, has the greatest voltage difference across it?
Explain.
YOU TRY IT HERE FIRST !!!
Page 1 of 3
Physics 110 Problems - My Solutions
Dr. Hulan E. Jack Jr.
Ch13 Q13 Two resistors are connected in series with a battery as shown in the diagram. R1, is
less than R2.
a.
Which of the two resistors, if either, has the greater current flowing through it? Explain.
b.
Which of the two resistors, if either, has the greatest voltage difference across it?
Explain.
Definitions, concepts , principles and Discussion
R1
Ohm’s Law
V = IR
Series circuits
current, I, is the same through all resistors .
(a)
ε+
R1
the voltage drop, V, across each resistor R is
given by Ohm’s Law as
(b)
V = IR.
So, the voltage drop across R1 is
V1 = I R1 ,
and that across R2 is
V2 = I R2 .
+
ε
-
R2
I
V1 = IR1
ε+-
But, R1 < R2 , hence R1/R2 <1.
So, V1/V2 = R1/R2 <1.
Yields V1 < V2 .
R2
I
(c)
The voltage drop is smaller for the small resistor. Or, oppositely , the larger resistor has
the greater voltage drop across it.
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V2 = IR2
R1
Relation between V1 and V2
R1 is less than R2 , that is R1 < R2.
So, V1/V2 = (IR1)/(IR2)
= (IR1)/(IR2)
Cancelling I gives
= R1/R2 .
R2
Physics 110 Problems - My Solutions
Dr. Hulan E. Jack Jr.
Ch13 Q13 Two resistors are connected in series with a battery as shown in the diagram. R1, is
less than R2.
a.
Which of the two resistors, if either, has the greater current flowing through it? Explain.
b.
Which of the two resistors, if either, has the greatest voltage difference across it?
Explain.
Basic Solution (Minimum Expected from the student)
a.
This is a series circuit. In a series circuit the same current flows though all series resistors
because there are no alternate paths.
b.
From Ohm’s Law, V=IR, the larger resistor has the greater voltage difference across it.
So, R2 has the greater voltage drop.
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