Transcript The_Force_Exerted_by_a_Motor_Notes

Lesson 7
Objectives
• Design and execute an experiment to
determine the operating conditions that
produce the maximum force from a motion.
• Analyze experimental data.
• Write a conclusion based on experimental
evidence.
• Measure the force that a motor exerts under
the best operating conditions.
Getting Started
• What is an independent variable?
• What is a dependent variable?
• Look at the model displayed by the teacher
and identify each part.
• A. How many washers can the motor lift?
• B. Can you think of anything that would
affect the motor’s ability to lift the load
of washers? If so what is it?
Vocabulary – Lesson 7
• Series Circuit: When batteries are arranged with terminals
connected from positive to negative to positive
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All electrons flow through a single path.
Voltages combine.
More current is produced.
Energy is more rapidly delivered to the motor.
It makes the motor more powerful.
If one battery discharges, the circuit does not work.
Vocabulary – Lesson 7
• Parallel Circuit: When batteries are arranged with terminals
connected from positive to positive and from negative to
negative
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There is more than one path for electrons to travel.
Voltage is the same as a single battery.
There is a small amount of current.
Energy is transformed at a slower rate.
Each battery lasts longer.
If one battery runs down, the others continue to supply energy.
Vocabulary Con’t
• Electric Motor: A device that transforms
electrical energy into mechanical energy.
• Voltage: The difference between electrical
potential energy between the two places in a
circuit.
Vocabulary – Lesson 7
• Several energy transformations take place in this
lesson.
• Energy is stored in the bonds between atoms. This energy is
known as chemical energy.
• Chemical energy is transformed to energy that causes electrons to
move. This is a transformation to electrical energy.
• The flow of electrons is electricity.
• Electrical energy is transformed into energy that runs the motor.
This energy in moving objects is mechanical energy.
L7
Notes: Parallel Circuits
Parallel Circuits:
• Are hooked up positive to positive and
negative to negative
• If one battery goes out, the other batteries
will still work to create a current because
there are several different paths for the
electrons to travel.
Parallel Circuits
• The voltage across a parallel circuit is equal to
the voltage of one battery because each
battery offers a small amount of current,
dependent on how many batteries are hooked
up.
• The energy is used at a slower rate which
causes each battery to last longer than it will
in a series circuit.
Parallel Circuits
• The motor will work as though it were
connected to one battery, but it works for a
longer time than it would if it were connected
to only one battery.
Series Circuit
• Series circuits are hooked up positive to
negative to positive, etc.
• There is only one path for electrons to flow in
a series circuit, so if one battery goes out, all
the circuit will not work.
• The strength of the circuit will only be equal to
the voltage of one battery, so it’s not a very
strong circuit.
Series Circuits
• The voltage of a series circuit is equal to the
sum of the voltage of all the batteries in the
circuit.
• The batteries in a series circuit will not last as
long as the ones in a parallel because the
voltage of all batteries is being used.
Series Circuits
• This type of arrangement will offer the
strongest current with the highest voltage and
delivers energy to the battery quicker making
the motor more powerful than if operated by
one battery.
Lesson 7
Question – Lesson 7
• What are the conditions that produce the maximum
force from a motor?
• What arrangement of string and batteries will allow
the motor to produce the most force? Will the
number of batteries affect the force of the motor?
• Will the arrangement of string, number of batteries,
and arrangement of batteries affect the maximum
force a motor will exert?
• Lesson 7
• If _________________,then __________
because _________________.
• Lesson 7
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Materials
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Experiment Steps
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1. Use a series circuit, string wrapped around the
nail. Change the batteries using one, then two,
then three. Record the maximum # of washers
each # of battery trial picks up.
• 2. Repeat #1 using a parallel circuit
• 3. Use a series circuit, string wrapped around
pulley. Change the batteries using one, then two
then three. Record the maximum # o washers each
battery trial picks up.
4. Repeat using a parallel circuit
5. Compare data and choose optimum arrangement
of batteries, circuit and string.
• Lesson 7
Diameter v. Number of
Washers Lifted (Force)
DIAMETER
Plastic pulley (large
diameter)
Nail (small diameter)
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NUMBER OF WASHERS LIFTED
( one battery)
Arrangement and Number of Batteries
v. Number of Washers Lifted (Force)
Number of
Batteries
Number of washers lifted
Series
Parallel
Arrangement
Arrangement
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2
3
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Maximum force exerted by the motor: ______________________
• Lesson 7