Technical data

24
hm’s Law
elationship of Power to I with a Constant R
roject Objectives:
• To show the use of the power formula by demonstrating how power is related to current squared
for a set resistance.
• To obtain practice in connecting circuits and using a DMM to make measurements.
ems Needed:
- Electronics Trainer - Digital multi-meter
- Jumper Wires - 10k  resistor
rmula states
making component
O
R
P
It
• While completing this project, keep in mind that the power fo
• Be sure to disconnect power when connecting meters and
circuit!
that (P = E x I)
changes to the
Experiment
1. Connect the circu it shown in figure 7-1.
______________
sured values of V and I a
V
A
until I equals 1/2 its original value.
e new voltage and calculate P using both formulas.
V I now = _____________________µA
____________________ mW
___________ mW
issipated w was double the value of current.
6. that power is proportional to I
2
when the resistance remains
power dissipation will increase by
(b) 2 (c (d) 4
7. er must decrease to
8. inal 14V value)
__________ mW
were applied?
___________
+
2. Adjust the applied voltage (V
A
) to 14 volts.
3. Break the circuit and insert an ammeter to measure
the current.
I = __________ mA
4. Use the mea nd calculate P
using the power formula.
P calculated =
_____________________ mW
5. Decrease
Measure th
V now = _____________________
P calculated using the formula (P = V x I) _
P calculated using the formula (I
2
x R) __________
P calculated is ___________ the power d hen I
(a) 1/2 (b) 1/4 (c) 1/8 (d) 1/16
We can conclude from this
unchanged. So if the current in a circuit doubles, the
______________ times. (a) 1
If the current in a circuit decreases to one-third its value, the pow
) 3
______________ its value. (a) 1/3 (b) 1/4 (c) 1/6 (d) 1/9
What would happen if V
A
was changed to 4.67 volts (approximately 1/3 the orig
New
V
A
= ___________________ V V x I now = ________
I
CALC
= ____________________ µA I
2
x R now = _________________ mW
Is the power approximately one-ninth that when 14 volts
−
10kΩ
V
Figure 7-1
A