current and voltage grade 8
DESCRIPTION
TRANSCRIPT
Current and Voltage
What is the difference between current and voltage?
?
Electric Current•Is the measure of the number of electrical charges passing through a cross-section of a conductor in a given timee-
Electric Current
A French physicist who made important contributions to the theory of electricity and magnetism
•the symbol is capital letter I•the unit is A (ampere)
• Ampere (A) is named after Andre-Marie Ampere
Electric Current
•Is use to measure electric current in a circuit.
A Multi-meter
How to Use Multi-meter in testing current?•The positive terminal of the multi-meter is connected to the positive terminal of the circuit and the negative terminal of the multi-meter is connected to the negative terminal of the circuit.
Voltage•It is the energy that makes the charges move in a closed circuit
Voltage
He invented the voltaic pile, the forerunner of what we now call dry cell
•the symbol is capital letter V
•the unit is V (volt)• Volt (V) is named after Alessandro Volta
How to Use multi-meter in testing Voltage?
•The voltmeter is connected across a load in a circuit.
•If voltage is needed for charges to flow, how does the amount of voltage affect current?…let’s find out in the activity…
Current and
Voltage
Objectives:1.To measure the electric
current and voltage in a circuit using an ammeter and voltmeter respectively
2.To determine the relationship between electric current and voltage
Materials:• 1 ammeter• 2 dry cells (1.5V)• 4 connecting wires• 1 bulb• 1 bulb holder• 1 switch
Procedure #1:1. Construct a simple circuit
using a dry cell, a bulb, a switch and a multi-meter. Close the circuit by turning on the switch. Observe the bulb and the multi-meter. Record the multi-meter reading in table 1. Upon completion the task, switch off the circuit.
Procedure #1:
.
Ammeter connected in a circuit
Ammeter connected in a circuit with one dry cell
Q1. What is the reading on the ammeter?
Procedure #2:Add another dry cell to the circuit. Record the electric current measurement in Table 1. Once the task is done, turn off the switch.
Procedure #2:
Ammeter connected in a circuit with two dry cells
Q2. Compare the brightness of the bulb with one dry cell to its brightness when there are two dry cells in the circuit.
Q3. What is the ammeter reading this time?
Q4. What can be inferred about the current passing through the bulb?
Procedure #3:Connect the voltmeter as shown in figure 5. Switch on and record the voltage in Table 1. Once the task is done, turn off the switch.
Voltmeter connected in a circuit with one dry cell
Q5. What is the voltmeter reading?
Procedure #4:Add another dry cell to the circuit. Record the voltmeter reading in Table 1. Observe the brightness of the bulb. Once the task is done, turn off the switch.
Voltmeter connected in a circuit with two dry cells
Q5. What is the voltmeter reading?
Q6. Describe the brightness of the bulb.
Q7. What is the voltmeter reading this time?
Q8. What can you inferred about the voltage across the bulb?
Q9. Refer to the table 1, how are voltage and current related?
Thank you for listenin
g!
Thank you for listenin
g!
Thank you for listenin
g!