Ohm’s Law
Would this work?
1.
2.
Yes
No
50%
1
50%
2
Would this work?
1.
2.
Yes
No
50%
1
50%
2
Would this work?
1.
2.
Yes
No
50%
1
50%
2
Parts of a circuit (review)
Voltage (V):
Current (I):
Resistance (R):
Human circuits activity #1
 In
your lab groups, build a HUMAN circuit
that includes the following:


Battery (power source)
3 Light bulbs in SERIES
Human circuits activity #2
 In
your lab groups, build a HUMAN circuit
that includes the following:


Battery (power source)
3 Light bulbs in PARALLEL
Human circuits activity #3
 In
your lab groups, build a HUMAN circuit
that includes the following:




Battery (power source)
Light bulb
Ammeter (to measure current)
Voltmeter (to measure voltage)
Debrief activity:
Measuring voltage:
Voltmeter must be
placed in PARALLEL
with resistor
Measuring current:
Ammeter must be
placed in SERIES
If the voltage is increased but
the resistance stays the same,
what happens to the current?
1.
2.
3.
It increases
It decreases
It stays the same
Current is directly proportional to voltage
If the resistance is increased but
the voltage remains the same,
what happens to the current?
1.
2.
3.
It increases
It decreases
It stays the same
Current is inversely proportional to resistance
So . . .
Ohm's law states that the electrical
current (I) flowing in an circuit is
proportional to the voltage (V) and
inversely proportional to the resistance
(R).
Ohm’s Law
Voltage = Current x Resistance
V = IR
Voltage:
measured in
Volts (V)
Current: measured
in Amps (A)
Resistance:
measured in
Ohms (Ω)
Practice Problem
A lightbulb with resistance of 100  is
plugged into a 120 V outlet. What is the
current flowing through the bulb?
Ohm’s Law Lab
 Part
1:
 Part
2:
What to do when I finish?
1.) Tidy up lab station and turn in lab to
group folder
2.) Go to the PHET website and build
various circuits (your choice). You must
measure current, voltage, and resistance for
each circuit. Draw a circuit diagram and
record current, voltage and current.
What would the effect be on a person if
they stuck their finger into a regular wall
outlet that supplies 120V (don’t try this at
home) with completely dry skin
(R=100,000ohms)?
25%
1.
2.
3.
4.
25%
25%
2
3
25%
12,000,000 Amps
8333 Amps
0.0012 Amps
No current
1
4
What would the effect be on a person if
they stuck their finger into a regular wall
outlet (again don’t try this at home) after
sitting in a bathtub full of salt water
(R=100ohms)?
25%
1.
2.
3.
4.
25%
25%
2
3
25%
12,000 Amps
1.2 Amps
0.83 Amps
No current
1
4