10/06/15
Electricity
Electricity is always part of our lives. Many of our activities involved electricity, like watching TV or charging your phone or even light up your house(light bulbs). Imagine a world without electricity, it would be like the stone age right?
In this module, you will learn more about electricity. There are three quantities that you should be familiar with in the study of electricity. These are electric current, voltage, and resistance. You will use the relationships among these quantities in
learning about circuit connections. You will also learn that some of the safety precautions you have been warned about can be explained by the relationships among voltage, current, and resistance.
Electric Current
In your past grades you learned that a circuit is any arrangement of an energy source, connecting wires, and a load (bulbs). You also learned that a complete or a closed circuit provides a path for electrical charges to flow. Electric current is a measure of the number of electrical charges passing through a cross-section of a conductor in a given time. The direction of conventional current or simply current is from the positive terminal of the battery to the negative terminal.
Voltage
In a circuit, work must be done on the charges to make them move. The battery supplies the energy in electric circuits. The chemical energy in the battery is transformed to electrical energy. This electrical energy moves the charges in a circuit. A battery consists of several dry cells or wet cells. Both dry and wet cells contain a conducting medium called electrolyte. The batteries we use in flashlights and watches are dry cells. The symbol for voltage is capital letter V. The unit, volts (V), is named after the Italian physicist Alessandro Volta who invented the voltaic pile, the forerunner of what we now call the dry cell.
A voltmeter measures voltage. The voltmeter should be connected across the load being tested. The positive terminal of a voltmeter is connected to the positive terminal of the bulb while the negative terminal is connected to the negative terminal of the bulb.
10/20/15
Activity 1: Current and Voltage
Objective: After this activity, you should be able to:
· Measure current and voltage using an ammeter and voltmeter.
· Determine the relationship between current and voltage
Materials:
· 1 ammeter
· 2 Dry cells
· 4 connecting wires
· 1 bulb
· 1 voltmeter
· 1 switch
· 1 bulb holder
Procedure:
Assemble a simple circuit using a dry cell, a light bulb and holder, wires and ammeter.
· If you turn on the switch, you would get a reading of: at least 0.39 in the ammeter.
· The reading increased to at least 0.9 when another dry cell is added.
Number of Batteries
Voltage
Current
1
4.52V
9
2
5V
10
· Comparing the brightness of the bulb will help you find out that two dry cells make the bulb glow 0.48x brighter
In activity 1, the current/voltage in circuits were compared. You observed that both recorders have greater readings in the circuit with more dry cells. This activity shows voltage and current and voltage increase. However, circuits aren’t just about voltage and current, there are other components too. Like load, a load converts electricity to light, heat and mechanical motion.
Resistance
When electricity flaws through wires and loads, they encounter resistance or a hindrance to their movement. Its symbol is the capital letter R. The unit Ω is named after German physicist, George Simon Ohm.
Activity 2
Current and Resistance
Objective: Be able to understand the relationship between current and resistance.
Materials:
· 1 ammeter
· 2 Dry cells
· 4 connecting wires
· 1 bulb(2.5v)
· 1 voltmeter
· 1 switch
· 1 bulb holder
Procedure:
Assemble a simple circuit using a dry cell, light bulbs and holders, wires and ammeter.
Number of Bulbs
Current
1
2.5
2
1.5
3
0.9
· The current decreases as the bulbs were added.
· Negative/Positive points balance the current
· More Resistance, Lesser Current.
10/27/15
Activity 3: What's the Connection?
Objective:
Understanding how loads work
Similarities of circuit connection
Materials:
Voltometer
Circuit A:
Identical light bulbs with holder
2 Dry cells
Circuit B:
Connecting wires
2 Light bulbs with holder
2 Dry cells
Procedure:
Construt a series circuit using 3 connecting wires, 2 identical light bulbs, and 2 batteries. Then unscrew one of the lightbulbs. You will see that all the lightbulbs will go off.
The design of the light bulb circuit:
The circuit contains 1 path and 3 wires.
The circuit will turn off if one the light bulbs is removed because every component is connected in one path.
Construct a parallel circuit using 3 connecting wires, 2 identical light bulbs, and 2 batteries. Then unscrew one of the lightbulbs. You will see that only one of the lightbulbs will go off.
The design of the light bulb circuit:
Circuit
Voltage Drop
Voltage Across both Bulbs
Bulb 1
Bulb 2
A
1.0
0.5
1.5
B
1.5
1.5
3
Explaination for the expirements
Circuit A: Series Connection
The circuit, the materials used to make the connection only takes one path. If one of the components are removed, a gap is created and turns the entire circuit off.
Circuit B: Parallel Connection
The circuit, the materials used to make the connection takes two paths. If one of the components are removed, a gap is created, but it doesn't turn the entire circuit off.
11/03/15
Activity 4: After performing this activity you should be able to:
· Describe the heating effect of the current of electricity.
· Example short circuits and its effects
· Explain safety reasons involving electricity
Materials
· A.
o 2 dry cells
o 2 connecting wires
o Fine strands of copper wire (20 cm long)
o 2 blocks of wood
· B.
o 2 connecting wires
o 2 dry cells
o 1 bulb with holder
Procedure A:
· Place the wood blocks side by side. Then place them with masking tape.
· Place thumbtacks on each wooden block.
· Wrap the copper wires, leaving two free ends on the same block.
· Place the candle on the copper wires.
· Connect the free ends and keep the circuit closed for 30 seconds.
· Disconnect the battery.
o You can see that the candle heats up due to the electricity inside the copper wires.
o The amount of electricity increases as the dry cells were added.
Procedure B:
· Construct a circuit with wires and 2 dry cells.
· Remove the insulation and observe.
o You will see that the bulb short circuits and burns out when insulation is remove.
o Electrocution is the effect of the short circuit.
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