Download Current - St John Brebeuf

Name_______________________
Date_____________________
Block ____
Ohm’s Law- A Calculating Personality!
Complete the following table. The table has been partially completed to help you.
Name and Abbreviation
Current
Symbol
(A)
Unit
Meter used for
measurement
Formula
I
V= I x R
____________ (R)
ohm
Provide two calculations to prove what happens if a variable is changed in each question.
The first one is done for you.
1. What happens to the current if resistance is increased in a circuit?
I = V/R
I=6/3
I=2A
The current DECREASES
I = V/R
I = 6/5
I = 1.2 A
2. What happens to the voltage if resistance is increased in a circuit?
_________________________
3. What happens to the voltage if resistance is decreased in a circuit?
_________________________
4. What happens to the current if resistance is decreased in a circuit?
_________________________
5. What happens to the voltage if current is decreased in a circuit?
_________________________
6. What happens to the voltage if resistance is decreased in a circuit?
_________________________
7. What happens to the resistance if current is decreased in a circuit?
_________________________
8. What happens to the resistance if voltage is decreased in a circuit?
_________________________
Complete the calculations. Be sure to write out the equation, and to include the units!
1) What current would flow through a resistor
of 20 ohms connected to a 12 V supply?
5) What supply voltage would be needed to
provide a current of 1.2 A through a 40 ohm
resistor?
2) What current would flow through a resistor
of 40 ohms connected to a 10 V supply?
6) A resistor allows a current of 0.6 A to flow
when connected to a 9.6 volt supply.
What current would flow if the same resistor
was connected to a 12.8 V supply?
3) A 100 ohm resistor is connected to a 20 V
supply. What current flows?
7) Calculate the voltage supply needed to
produce a current of 12A when used with a
48 ohm resistor
4) What value of resistor would be used to
permit a current of 0.2 A to flow using a 6V
supply?
8) Calculate the voltage across a 300 ohm
resistor when a current of 0.004 A flows
through it.
9) Find the size of resistor which would allow
limit the current to a value of 0.02 A when
connected to an 8 V supply.
12)
An 80 V potential difference is measured
across a light bulb that has a resistance of 16 Ω.
a) What is the current through this light bulb?
10) Calculate the current which will flow when
(b) If the light bulb was replaced by a bulb with
twice the resistance, what would be the new current
through the bulb?
a total resistance of 500 ohms is placed in a
circuit which has a 15 volt supply.
11) A current through a resistor in a circuit is
1.5 A. If the potential difference across the
resistor is 6V, what is the resistance of the
resistor?
13) What is the resistance of a toaster if a current of
12.5 A flows through it when it is connected
to 120 V?
14) A flashlight bulb has a resistance of 4.0 Ω.
What current passes through the bulb if it is
connected to 3.0 V?
15) A light bulb has a resistance of 90 Ω. What
current flows through the bulb when it is connected
to 120 V?
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Use the graph below to answer the questions that
follow.
1. (a) What happens to the voltage as the current
increases? ____________________________
(b) What does this suggest about the relationship
between voltage and current?
__________________________________________
2. According to the graph, what happens to the
voltage when the current is doubled?
___________________________________________