JMJ
1. Know all vocabulary from vocabulary sheet. Besides possibly matching or multiple
choice questions matching terms and definitions, answers questions that include those
terms as the context for the questions or the answers.
Current
Ohm’s Law
Resistor
Tesla (T)
Amperes (amps, A)
Potential Difference
Circuit
Electric potential
Voltage (volts, V)
Series circuit
Multimeter
Resistance (ohms, Ω)
Parallel circuit
Calculations and lab skills
2. Use formulas (provided) to calculate voltage, current, and resistance:
Ohm’s Law: V = I R,
V = I R Voltage = Current x Resistance, I = V/R, Current = Voltage/Resistance
R = V/I Resistance = Voltage/Current
3. Formula for the strength of a magnetic field B = 0nI, B = magnetic field,
0 = 4 x 10-7 Tesla-meters/amps,
n = N/L (N = number of turns of wire, L = length of coil in meters), I = current in amps,
4. Interpret graphs, make graphs, and identify correct graphs: including correctly labeled
axes and correctly spaced intervals on axes. Identify independent and dependent
variables from fact scenarios (similar to investigation scenarios) and know which axis is
associated with each. Line of best fit graphs and line graphs.
5. Interpret schematics of electrical circuits and identify the various parts shown in the
schematic, including positive and negative terminals of a battery, resistor, voltmeter,
ammeter, series circuits and parallel circuits.
6. Match a photograph or sketch of a circuit with the correct schematic for the circuit.
SDR Background 2, 3, 5, 13, 19, 21-22, 24, 33, 34, and 39
Multiple choice questions regarding:
1. Relationship between voltage and current
2. Effect of a resistor on current in a circuit
3. Relationship between voltage, current, and resistance as described by Ohm’s law, V = IR
4. Interpreting data from tables relating to voltage, current, and resistance
5. Relationship between the dimensions of a resistor and its effect on current
6. Effect of length of a resistor on current
7. Effect of cross-sectional area on a resistor on current
8. Magnetism
9. Electromagnets, how they work and how they are made
10. Relationship between flow of electric current in a wire and the magnetic field created by
the flow
11. Relationship between the strength of an electromagnet and the current flowing through a
circuit
12. Ways to change current flowing through a circuit thereby changing the strength of an
electromagnet – change number of batteries or change the number of turns of wire
wrapped around the nail
Concepts to know:
There is a direct relationship between voltage and current, when one changes the other
changes the same way.
In a circuit, the greater the resistance, the lower current and vice versa.
Voltage and current are proportionally related and the ratio of voltage to current is
resistance.
Increasing voltage increases the amount of current in a circuit while resistance remains
constant, regardless of the size of resistor.
Ohm’s Law is true when the voltage is held constant while the amount of resistance
changes.
Increasing the number of resistors has the same effect as changing the diameter or the
length of a resistor.
Increasing the length of resistor (resistors in series) increases resistance and decreases
current.
Increasing the cross-sectional area of resistor (resistors in parallel) decreases resistance
and increases current.
The magnitude of an electromagnet’s magnetic field is directly related to the number of
coils of wire around the magnet, the length of the coil, and the amount of current flowing
through the wire.
Increasing current in an electromagnet causes an increase in the magnetic field, allowing
the magnet to attract a greater number of objects. Increasing the number of coils of wire while
keeping the length of the coil constant increases the magnetic field as well.
Unit Summary
The change in current in a circuit is directly proportional to the change in its voltage. As
voltage in a circuit increases, current increases but the resistance to the flow of current remains
constant. As the number of batteries in a circuit increases, the voltage increases and the current
increases, but the resistance remains constant as long as the resistor is not changed.
In addition, the change in current in a circuit is inversely proportional to the resistance.
As the resistance in a circuit increases, the current decreases. In circuits with different voltages
and different resistances, the circuits with the greater resistance have a lower current than the
circuits with the lesser resistance, no matter how much voltage is passing through the circuit.
The relationship among voltage, current, and resistance is described by Ohm’s Law,
V = IR or R = V/I.
Resistance is the ratio between the voltage and the current in a circuit. As voltage
changes, current changes in proportion to the voltage. However, resistance remains constant
provided no changes are made to the components of the circuit that provide resistance.
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When voltage is held constant, current changes only if the amount of resistance in the
circuit changes. Increasing resistance by changing resistors results in a decrease in current
proportional to the change in resistance, but the voltage remains constant. Placing two 1000 Ω
resistors in series causes current to decrease by approximately one-half. At the same time,
resistance doubles. Placing two 1000 Ω resistors in parallel causes current to double while
resistance decreases by one-half. In each case, the change in current and the change in resistance
are inversely proportional and voltage remains constant. Ohm’s Law applies regardless of
whether there is one resistor or many resistors. Ohm’s Law also applies regardless of whether
multiple resistors are placed in series or in parallel.
Increasing the length of a resistor by placing two equal resistors in series doubles
resistance. This causes current to decrease by half. Increasing the cross-sectional area by
placing two equal resistors in parallel decreases resistance by half. This causes current to double.
Therefore, increasing the length of a resistor increases the amount of resistance and decreases
current, while increasing the cross-sectional area decreases the amount of resistance and
increases current.
There is a direct relationship between electricity and magnetism. The flow of current
through a wire generates a magnetic field perpendicular to the wire. As the amount of current
flowing through the wire increases, the magnitude of the magnetic field increases. When the
magnetic field increases, the electromagnet can attract more paper clips.
The strength of an electromagnet is affected by the number of turns of wire in the coil
over a specific length. The strength of an electromagnet is also affected by the amount of current
flowing through the wire. As the number of turns of wire in the coil increases, the strength of the
electromagnet increases. Decreasing the number of turns of wire decreases the strength of the
electromagnet. Increasing the current also increases the strength of the electromagnet.
Decreasing the amount of current decreases the strength of the electromagnet.
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