Investigating the Resistance of a 12 Volt Bulb When the Current Changes
Prediction: I predict that as the current increases the temperature of
the lamp will also increase; therefore the resistance will also
increase. I know this because I have read it in the AQA syllabus.
Plan
Safety: I need to ensure the safety of myself and others by making
sure that the experiment is conducted accurately and safely.
- Apparatus should be placed in a safe place and put away safely.
- Electrical plugs should be switched off after use.
- The area should be kept dry and taps should be switched off.
Variables: I will only be changing the current by moving the variable
resistor.
I will repeat the experiment twice so that I can be sure of my
readings and see if anything has changed or gone wrong. I will take 12
readings at 0.1 amps intervals.
Apparatus:
o Voltmeter
o Ammeter
o Variable resistor
o 12 volt lamp
o Battery pack (set at 12 volts )
o Leads
Method:
1. Using the apparatus listed above I will set up the following
circuit:
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[IMAGE][IMAGE][IMAGE][IMAGE]Key
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[IMAGE]Variable resistor
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[IMAGE][IMAGE]Ammeter
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Lamp
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[IMAGE]Voltmeter
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[IMAGE][IMAGE][IMAGE]Battery pack
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[IMAGE]Lead
2. I will do a preliminary test to find the range of current in
amps. I will do this by moving the variable resistor to its lowest
and highest points and noting down the amps. In this case the
lowest point is 0.5 and the highest is 1.6 amps.
3. I will start with 0.5 amps, working systematically, I will note
The experiment consists of two people that take part in a study of memory learning, one of them referred to as the "Teacher" and the other as the "Learner." The experimenter explains that the study's main goal is to observe the effect of punishment on learning. The learner will be seated in something similar to the electric chair, his arms will be strapped and an electrode will be attached to his wrist. The learner will be told that he will be tested on his ability to remember the second word of a pair when he hears the first one again. If he makes a mistake, he will then receive electric shocks of increasing intensity.
Volume's Effect on a Copper Sulphate Solution We are trying to find out if the current though a copper sulphate solutions volume is increased. To find this information out I shall perform an experiment using the following equipment; · 1 power pack · 1 beaker · 2 carbon rods for anode and cathode · 1 ammeter · 1 measuring cylinder · 2 crocodile clip wirers I shall also be using 60cm3 volume of copper sulphate in my preliminary results to decide upon the concentration of copper sulphate and the voltage I shall use. The following diagrams show the step by step process in which I will do my experiment; [IMAGE] [IMAGE] [IMAGE] [IMAGE] I will take 10 readings from 10cm3 to 100cm3. I will repeat my experiment to give my experiment a fair average. I will keep the power pack the beaker the carbon rods the crocodile clips the ammeter the concentration of copper sulphate and the measuring cylinder the same each time I do the experiment this experiment.
3. Plug power supply into the mains and switch on. 4. Check that the voltmeter is showing positive. Length-cms Amps-I Volts-Potential Difference Resistance-Ohms 0 4.85 0.04 0.008247423 10 2.38 0.46 0.193277311 20 2.08 0.67 0.322115385 30 2.38 1 0.420168067 40 2.2 1.22 0.554545455 50 1.95 1.49 0.764102564 60
From this I can tell I can use 3 volts and resistance wire that is
equation V = IR. V - volts, I - current and R - resistance. I plotted
Variables --------- During the experiments, the water will be heated using different spirit burners containing different alcohols. I will be able to change different parts of the experiment. These are the. Volume of water heated:
Two electrical wires * Stopwatch * Thermometer Method I put a piece of Elodea Canadensis (pond weed) in a test tube and covered it with water. The test tube was then placed in a beaker with a thermometer so that the water stayed the same temperature, this was then placed in a cardboard box with a bulb attached to a voltmeter by the electrical wires so that I could concentrate how much light the plant got. I varied the voltage (intensity) of the bulb and counted how many bubbles of oxygen were created at each voltage in one minute. I tested each voltage three times for accuracy for a minute each time. Results Preliminary Experiment Amount of bubbles Light intensity (lux)
The current flowing through the wire will be recorded to the nearest 0.01A, using an ammeter placed in series with the circuit.
The purpose of the lab was to show the effect of temperature on the rate of
I also decided to use a wooden block to keep hold of the wire, because
= F The circuit was set up as in the circuit diagram overleaf with a power source of 5 Volts, an ammeter, crocodile clips (holding wires). and a variable resistor in series and a voltagemeter in parallel with the wires. The sand is F Nickel chrome wire was then measured to discover the cross section. width with a micrometer screw gauge and this was recorded and the cross sectional areas were calculated using €r2 multiplied each time by the number of wires used, each bit of wire was cut into lengths of 30.
There fore less current passes through with the same voltage. Simply it is how hard it is for the electrons to pass through the wire. Temperature: When the metal wire is heated , more energy s given to the atoms, therefore they vibrate more. From this there is a greater chance of collisions with the electrons and they are impeded more, therefore less charge is passed by the electrons and the resulting current is reduced. This means while conducting the experiment the temperature of the wire must be kept constant to maintain a safe and fair test.
-Voltmeter -Variable resistor -Power Supply -Various diameters of wire -Crocodile clips -Metre ruler [ IMAGE] Diagram:.. Secondary Source - (Obtained in A-level PHYSICS by Roger Muncaster). Page 536 - "The 'Page The electrical resistivity of a material is defined by R = L / A Where R = Resistance of some conductor(Î).
In the experiment there are several possible ways of changing the electric current such as changing the voltage or the position of the electrodes within the electrolysis cell. However, it was found from preliminary work that the most effective way to change the current was to change the concentration of the acid solution. The preliminary work showed that the greater the concentration of the acid, the greater the current. Ohm's law states that R(resistance) =
Before conducting my experiment I will research into, amongst other things, the factors that affect the rate of a reaction. This is so that I may enough information to understand the effect of temperature on the rate of a reaction and also gain appropriate understanding to make a suitable prediction as to what the outcome of my experiment will be.