Current Metals and graphite are conductors of electricity.
When metals such as copper
and aluminium are drawn into wires the electrons within the atoms of the wire
There are two forms of electricity: static and dynamic electricity. gain energy from a power source and they begin to vibrate. The electrons
closest to the power source vibrate first and this causes a chain reaction of
Static electricity is the result of an imbalance between negative and positive
vibrations which affects the other electrons. This is referred to as the flow of
charges in an object. These charges can build up on the surface of an object
until they find a way to be released or discharged. One way to discharge them electrons and it can only occur within a closed circuit.
is through a circuit. The following are examples of static electricity:
In a closed circuit, current flows in one direction. The flow of current in your
physics text refers to the CONVENTIONAL FLOW of current where
1. Rubbing a balloon on your clothes and then placing it above your hand
electrons leave the positive terminal of the cell or battery and enters the
causing the hairs upon it to rise.
negative terminal of the cell or battery. However, the actual flow of electrons
2. Walking across the carpet in your socks and receiving a shock from a door around a circuit occurs from the negative terminal of the power source into the
positive terminal of the power source. The latter is referred to as ELECTRON
knob.
FLOW of electric charges which is the correct idea behind how electrons
actually flow around a circuit but because all of the equations involving
3. Constant rubbing of clouds to produce lightning
electricity are based on the CONVENTIONAL FLOW of current, it is still used
All materials contain positively and negatively charged particles known as to describe the flow of current through a closed circuit to avoid confusion today.
protons and electrons respectively. A body is neutral if its positive and negative
There are two types of circuits, series and parallel circuits. In a series circuits,
charges are equal in number. If it contains excess positive charge, it is
there is only one pathway for current to travel, while in a parallel circuit there
positively charged, if it contains excess negative charge, it is negatively
are more than one pathway to travel.
charged. On a neutral body, charges are not shown.
There are four methods which cause static electricity:
1. Friction
2. Conduction
3. Induction and
4. Polarization
Dynamic electricity refers to moving electric charges. There are two types of
electric charges, positive and negative electric charges. Like charges repel as in
two positive charges will repel each other, two negative charges will repel each
other while a positive and a negative charge will attract each other. All matter
is made up of atoms. Atoms are comprised of subatomic particles, protons,
neutrons, and electrons. The positive electric charges are the protons while the
negative electric charges are the electrons. Neutrons have no charge, they are
neutral. In a series circuit if there is more than one component within the circuit and one
of them stops working this will cause a break in the circuit and therefore the rest
Dynamic electricity occurs in conductors because they contain mobile electrons. components will stop working. The advantage that a parallel circuit has over a
series circuit is that if there is more than one component within the circuit and The resistance of a conductor can be determined by measuring the amount of
one of them stops working this will not cause a break in the circuit and all of the current that passes through the circuit as the voltage is increased. From the
other components will continue to work. This is because as earlier stated, a information obtained a table of voltages and corresponding current can be
series circuit has only one pathway for current to flow while a parallel circuit tabulated and then the relationship (gradient) can be determined via a graph of
has more than one pathway for current to flow. current against voltage. The inverse of the gradient can then be used to
determine the resistance of the bulb that was placed within the circuit.
The S.I. unit of current is the ampere, A. An ampere refers to the amount of
electron that are flowing per second.
1 ampere = 6.24 × 1018 electrons flowing through a certain point per second.
Think of how water flows through a pipe.
Voltage is a difference in electrical potential energy, per unit of charge, between
two points. In other words, voltage is the push that drives the electric charges
(electrons) from an area of higher negative potential (negative terminal) to an
area of lower negative potential (positive terminal). Voltage is sometimes
referred to as potential difference and has an S.I. unit of V. Voltage, current
and resistance in a circuit are related where:
V=I×R
Resistance is the opposition to the flow of current through wires. The longer
and thinner a wire the more resistance electrons will meet in the wire.
Resistance has a unit of ohm, Ω. A simple metal wire will have a constant
resistance as long as its physical properties and conditions do not change. The
relationship was discovered by Georg Ohm and is called Ohm’s law:
The current through a conductor is directly proportional to the voltage or
potential difference across it.
Name: Diagram:
Date:
SBA: 13
Topic: Static and current electricity
Title: Resistance
Aim: To determine the resistance of a bulb in a series circuit
Equation:
R = V/I
Where R means resistance with units of ohms, Ω; V means voltage with units
of volts, V and I means current with units of amperes, A
Apparatus/Materials: power source, connecting wires, one light bulb and an
ammeter
Method:
1. A series circuit was set up a using a power source with multiple voltage
settings, ammeter and a light bulb as demonstrated in the diagram.
2. The voltage was set to 1 V and the amount of current flowing throughout the
circuit as well as the amount of voltage experienced across the component were
recorded.
3. Step 2 was repeated four more times at 2V, 3V, 4V and 5V.
4. Using the results obtained a graph of current against time to determine its
slope, R was generated.
5. To determine the resistance of the bulb the inverse of the slope was
calculated by dividing 1 by the slope where resistance = 1/slope.
Observations:
(Describe what you noticed here.) DIAGRAM SHOWING HOW LAB WAS EXECUTED
Data and Results: Discussion: (Use these questions as guidelines for writing your discussion in
paragraph form)
Table 1 showing how the voltage affected the current that was being passed
through a bulb Paragraph 1:
Define resistance giving its unit.
Amount of Current Paragraph 2:
Voltage of Power Voltage Across
Passing Through
Source (V) Component (V) Using your graph explain how altering voltage affects current as well as the
Circuit (A)
behaviour of the intensity of the light produced from the bulb.
Precautions:
1. All electrical instruments were handled with care.
2. All electrical instruments were handled with dry hands.
Limitations:
1. Poorly calibrated instruments such as the ammeter and voltmeter could have
lead to the documentation of inaccurate results.
2. The quality of the components used may have caused the documentation of
poor results.
Reflection: (How does this lab apply to everyday life?)
Calculations: (Show ALL calculation(s) performed) I now know why…..
𝛥𝑦 𝑦1−𝑦2 𝑦2−𝑦1
1. slope of graph, R = = OR Conclusion:
𝛥𝑥 𝑥1−𝑥2 𝑥2−𝑥1
In conclusion …
1
2. Average resistance across bulb = Ω
𝑅
Name: …………………………………………………………………………... Method:
Date: ……………………………………………. …………………………………………………………………………………...
SBA: ………….. ……………………………………………………………………………………
Topic: ………………………………………………………………………….. ……………………………………………………………………………………
Title: …………………………………………………………………………… ……………………………………………………………………………………
Aim: …………………………………………………………………………… …………………………………………………………………………………...
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Apparatus/Materials: …………………………………………………………
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Observations: Diagram:
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DIAGRAM SHOWING HOW LAB WAS EXECUTED
Data and Results: 1
2. Average resistance across bulb = Ω
𝑆
TABLE 1. ………………………………………………………………………
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Amount of Current
Voltage of Power Voltage Across Discussion:
Passing Through
Source (V) Component (V)
Circuit (A)
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Calculations: (Show ALL calculation(s) performed) …………………………………………………………………………………..
𝛥𝑦 𝑦₁−𝑦₂ 𝑦₂−𝑦₁ …………………………………………………………………………………..
1. slope of graph, S = = OR
𝛥𝑥 𝑥₁−𝑥₂ 𝑥₂−𝑥₁
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Precautions: …………………………………………………………………………………..
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Limitations:
Conclusion:
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Measurement and Manipulation – Observation & Recording – IV relationships
IV relationships a. Student’s ability to record observations and
to collect and organise data; observations and
1. Following instructions /1 data may be recorded in:
2. Uses basic laboratory equipment correctly /4 (i) Prose
power source (1) Written description of observations in the correct
wires (1) tense /1
ammeter (1) (ii) Table
and bulb (1) Appropriate headings /1
Title given /1
3. Sets up electrical circuit correctly /1 (iii) Graph
* Title for graph /1
4. Uses electrical circuit correctly /1 * Title axes labelled for both x and y /2
* Correct scales /2
5. Prepares material for observation or * Accurate plotting: /5
investigation correctly /1 All points plotted correctly (5)
1 -2 points plotted incorrectly (4)
6. Student’s ability to take accurate 3 -4 points plotted incorrectly (3)
measurements /1 5 -6 points plotted incorrectly (2)
7- 8 points plotted incorrectly (0)
7. Student’s ability to use appropriate units /1 * Fine points used /1
* Best fit line drawn /1
Total: /10
(b) Reporting
Student’s ability to prepare a comprehensive
written report on their assignments using the
following format:
(i) Date (date of experiment) /1
(ii) Aim (what is to be accomplished by
doing the experiment /1
(iii) Apparatus and Materials (all equipment
and materials
used in the experiment must be listed) /1
(iv) Method/Experimental Procedure (step by
step procedure written in past tense) /2
Total: /20
