STEP-UP 2011
Lesson Plan: Capacitance
Brian Heglund
Etowah High School
Advisor: Phil First
Ultra High Vacuum (UHV) at GT can analyze sample
surfaces with Leed and Auger.
Problem: Can this wire be used in the UHV without shorting
through the UHV components?
Abstract
Students learn theory of capacitors as summer research
experience is related anecdotally. Students apply knowledge to
design and construction of two separate circuits with
capacitors.
Alignment with GPS
College Board Performance Objectives:
College Board Performance Objectives:
● Define the ampere as the unit of electrical current.
● Distinguish between conventional flow and electron flow.
● State Ohm's Law for electrical components.
● Define the unit of resistance, the ohm.
● Calculate the resistance across a bank of resistors in series,
parallel, and combined.
● Discuss emf and its role in DC electrical theory.
● Distinguish between emf and potential difference.
● Define and describe voltage, current, and equivalent
resistance for resistors connected in series, parallel, and
combined.
College Board Performance Objectives:
● State Ohm's Law for an entire electrical circuit and apply it
to the solution of electrical problems involving internal
battery resistance and total resistance of the circuit.
● Calculate the total resistance of an entire DC circuit.
● Compute power loss in a given DC circuit.
● Determine the terminal voltage, given the emf of a battery,
its internal resistance, and the load resistance.
● Determine the potential drop across a resistance carrying a
given current.
● Define the factors that determine the resistance of a given
wire.
● Calculate the resistance of a wire given its resistivity, length,
and radius.
College Board Performance Objectives:
● Relate the potential difference across a resistor carrying a
current to its energy loss.
● Define the watt as the unit of electrical power.
● Determine the power loss across a given current carrying
resistance.
● Write and apply Kirchhoff's Rules for electrical networks in
the determination of unknown currents.
● Analyze multiloop circuits using Ohm's Law and Kirchhoff's
Rules.
● Calculate the equivalent capacitance of a number of
capacitors arranged in (1) series, (2) parallel, and (3) series
and parallel combination.
● Understand how to use ammeters, voltmeters,
galvanometers, and the Wheatstone bridge.
College Board Lab Objectives:
● Experimentally, demonstrate Ohm's Law with a voltmeter,
an ammeter, a rheostat, a source of emf, and appropriate
lead wires and draw a schematic diagram of an electrical
set-up, using appropriate symbols for the electrical
equipment used.
● Design an experiment to measure the resistivity of a
conductor.
● Design an experiment to measure the power loss across a
resistance.
● Design and conduct an experiment using two loops,
resistors in each loop, and several seats of emf.
● Design and conduct an experiment to find the resistance of
unknown resistors using the Wheatstone Bridge.
College Board Lab Objectives:
● Experimentally determine charge and voltage relationships
for capacitors in series, parallel, and combined networks.
● Design and conduct an experiment to measure the time
constant in an RC circuit.
Anticipated Learner Outcomes
● Demonstrate a comprehension of physical and
environmental reality by understanding how fundamental
physical principles underlie the huge variety of natural
phenomena and their interconnectedness.
● Demonstrate basic experimental skills by the practice of
setting up and conducting an experiment with due regards
to minimizing measurement error and by the thoughtful
discussion and interpretation of data.
● Demonstrate basic communication skills by working in
groups on a laboratory experiment.
●
http://www.ohlone.edu/instr/physics/courses.html
Rubric
experiment 1: full credit is given if the light bulb
illuminates
experiment 2: full credit is awarded if students
successfully experimentally determine breakdown
voltage of capacitor.
Background: Wire coating insulates current from traveling through other
conductors such as UHV components. When this occurs, a short circuit has
been created.
Background: Two strands of wire were tightly
twisted.
Background: At low potential difference, the insulative coating
prevents current.
Background: Voltage is less than air's breakdown
voltage - no current.
Background: When voltage is greater than the wire's voltage, the insulative
coating becomes conductive - current flows from one wire to the other, forming a
closed circuit.
Background: Voltage is greater than air's break
down voltage - air conducts the current.
Background: First I confirmed that the measuring instruments worked properly.
Background: Next I increased the voltage. If I exceeded the breakdown
voltage, a voltage drop would occur across the resistor.
Background
The wire was deemed safe when 1 kilovolt was achieved and
no breakdown occurred.
This is one way a capacitor can be modeled.
A capacitor consists of two conductors with an insulative
material between them. When a potential difference exists
between the conductors, capacitors store energy.
Background
Computer memory chips, or DRAM, use capacitors to store
information. Binary code can communicate all letters, numbers
and punctuation as ones and zeroes. A potential difference
causes charge build up on one of the plates to create this code. A
binary "1" or "on" is created when a potential difference exists
and charge is stored. A binary "0" or "off" is created when
there is no potential difference and no charge is stored.
Supplies
voltage source, wires, resistor, capacitor, light bulb, switch,
mulitmeter
Plan: Your assignment is to build a functioning
circuit like the one above. The light must illuminate.
Plan: It's your turn to experimentally determine the breakdown voltage of the
capacitor. Compare that to the accepted capacitor voltage rating. Let me check
off your configuration before you perform the experiment.
Summary
By hearing my about my summer research at Georgia Tech,
students will learn about capacitors and apply knowledge to the
design and construction of two circuits with capacitors.