LEARNING OUTCOME:
2f• measure voltages and amperages in circuits
**MEASURING CURRENT: page 274 (diagrams on page 488-490)
**CURRENT: (I) is the amount of charge that passes a point in a
conducting wire every second
**Measured by:
**1. galvanometer: units: milliamperes (mA or µA)
-measures very weak currents
-demo using a lemon with two wires
**2. ammeter:
units: amperes (A)
-measures larger/stronger currents
BOTH DEVICS HAVE TO BE PLACED WITHIN THE CIRCUIT TO
MEASURE THE CURRENT READING
LOOK AT PAGE 274 AT TABLE 4.2 AND 4.3 FOR COMMON READINGS
**LEARNING LAB: MEASURING CURRENT
**Problem: Does the electric current flowing through a circuit vary at
different points within a circuit?
Material: 6V battery, switch, 3.7V lamp, 4 leads and ammeter
**Observations:
A
C
Ammeter
Location
A
B
C
B
Ω
Electric Current (mA)
Switch Open
Switch Closed
Procedure:
1. Set up the above circuit
2. Place the ammeter in position A (between battery and switch)
3. Take ammeter reading with the switch open and then closed.
Record readings on chart.
4. Repeat step three with ammeter in position B and C
**Analysis:
1. What effect did opening and closing the switch have on the
current?
2. What is the role of the switch?
3. Explain what the electric current is at different places in the
circuit.
LEARNING OUTCOME:
2f• measure voltages and amperages in circuits
**MEASURING VOLTAGE:
**VOLTAGE OR POTENTIAL DIFFERENCE: is the energy push that
comes from the separated (+) and (-) charges. It is what makes the
electrons move.
Or
It is the difference in energy per unit of charge between 2 points in
a circuit.
**Measured by:
**1. voltmeter: units: volts (V)
-a voltmeter does not have to be part of the circuit to measure the
potential difference
**POTENTIAL ENERGY IS STORED ENERGY
**KINETIC ENERGY IS ENERGY ON THE MOVE
**ENERGY is measured in Joules (J)
LOOK AT PAGE 275 TABLE 4.4 AND 4.5
**LEARNING LAB: MEASURING VOLTAGE
**Problem: How does the voltage (potential difference) across different
components within a circuit compare?
Material: 6V battery, switch, two 2.5 bulbs, one 3.7V bulb, 6 leads, and
a voltmeter
A
**Observation:
B
E
Ω
Ω
D
C
Location of Voltmeter
A-around battery
B-around switch
C-lamp one
D-lamp two
E-both lamps
E with one bulb unscrewed
D with 3.7V lamp
Voltage (V)
Procedures:
1. Set up the circuit as shown above –use the 2.5V lamps and make
sure it works.
2. Connect the voltmeter around the source. Keep the switch
closed. One lead before the battery and one lead after the
battery.
3. Measure the voltage and record.
4. Repeat step two and three with the voltmeter at position B, C, D
and E and record results.
5. Replace lamp at position D with the 3.7V. Compare the
brightness of the 3.7V bulb with the original 2.5V.
6. Take the voltage in position D with the 3.7V bulb and record.
**Analysis:
1. What part of the circuit provided the electrical energy?
2. What part of the circuit used the electrical energy?
3. Compare the voltage across the battery (A) to the voltage across
the load (E). How does the energy supplied compare to the
energy used?
4. How does the potential difference across bulb C and bulb D
compare to across both bulbs (E)?
5. How did the brightness of the 2.5V bulb compare to the 3.7V.