.•.
Activity: 2
DC Measurements:
Group Number:
Date of Activity:
Resistance
Group Members:
Scope:
At the end of the exercise the students will be able to
•
Measure and Calculate resistance value.
•
Measure and Calculate net resistance of Series, Parallel and Compound
•
Expla in the effect of Short Circuit and Open Circuit on the net resistance.
circuit.
Resistance Measurements
1.
Set DMM as Ohmmeter by connecting positive meter lead (Red) to the Volts/Ohms terminal and
black meter lead to the Ground/Com, locate and press 0 sign button, you can select the range
(0, kO, MO) by pressing Hi or Low buttons.
aJ Change the range to Ohms, without connecting the test leads to anything, what does the displdy
read? Why?
bJ Connect the two test leads together, what happened? what is the reading now? Why?
2.
You are provided with four different resistances. For each resistor, determine
from the color code table (arrange Rl as lowest and R4 as highest)
Nominal
Nominal
Nominal
Nominal
Value
Value
Value
Value
of
of
of
of
Rl:
R2:
R3:
R4:
its nominal value
3,
Change the range of DMM to kG and measure the resistances by touching one probe to each
lead of the resistor.
Measured
Measured
Measured
Measured
Value
Value
Value
Value
of
of
of
of
Rl:
R2:
R3:
R4:
c)
Do the nominal and measured
values agree? Why?
4.
With both calculated and measured values, Verify that two resistors connected in series exhibit
an overall resistance equal to the sum of the two individual resistances. Do this for the pairs RlRZ, R2-R3, R3-R4, and Rl-R4. Comment on the result in each case.
5.
Verify that two resistors connected in parallel exhibit an overall resistance equal to the product
over the sum of the two resistances. 00 this for the pairs RI-R2, R2-R3, R3-R4, and RI-R4.
Comment on the result in each case.
6.
Drawa circuit with four resistances in parallel. Calculate net resistance.
•
7.
Connect all four resistances in parallel and measure the net resistance. Does calculated net
resistance agree with measured net resistance? Why?
d) The net resistance is smaller than the lowest resistance? Why?
8.
Connect the circuit as in fig below (compound
through terminal A and B.
circuit). Calculate and measure net resistance
A
R3
R2
B
R4
..
e) Find net resistance at terminal AB if Terminal A and B are short circuited? changed? why?
f)
Find net resistance at terminal A B if R4 is short circuited? changed? why?
g) Find net resistance at terminal A B if R3 is open circuited? changed? why?