Hydrochloric acid and calcium carbonate Essay Example for Free

Hydrochloric acid and calcium carbonate Essay Resistance is measured in ohms. A light bulb has resistance. The filament resists the flow of electricity, and glows white hot in doing so. The resistance causes the bulb to only allow a portion of the current available in the wall socket, to flow out. A 100-watt light bulb uses more electricity from the wall than a 60-watt light bulb because the filament in a 100-watt bulb has less resistance to it. This lower resistance allows more current to flow through the bulb, consuming more power, producing more work and making more light. This work, by the way, is called Wattage. If you multiply the voltage times the current answer is in watts. Prediction for length I predict that when the length of the conductor, in this case constantan, is increased, the electrical resistance will subsequently increase. This means that the resistance is directly proportional to the length. For example, when the length is doubled, the resistance is doubled, and when the length is tripled, the resistance is tripled. Therefore, by taking 3 lengths of 10cm wire and putting them in series, one by one, the resistance of the circuit should, at first, double, and then triple. Total Resistance = Resistance1 + Resistance2 + Resistance3 Total Resistance = 3 x Resistance This shows that the resistance is directly proportional to the length. This may happen because; a conductor is made up of a lattice of atoms surrounded by a sea of free electrons (found in the outer shell of the constantan atoms. ) The free electrons jump from atom to atom and form the net flow of electrons around a circuit. Before a power supply is switched on, the free electrons are simply bouncing around inside the conductor. However, once the power supply is switched on, the free electrons are pulled through the circuit towards the positive terminal, and pushed away from the negative terminal, therefore creating the net flow of electrons. This ensures that there is always the same amount of electrons in the conductor, in this case constantan, at any given time. However, constantan is made up of atoms, which are very tightly packed together, only moving in tiny vibrations. To flow around the circuit, the electrons must use a lot of energy to get through these atoms. They crash and collide into the atoms causing them to vibrate a lot more rapidly and vigorously. This vibrating causes a change in energy from kinetic energy to heat energy, or friction. As the atoms movement increases and the metal becomes hotter, the electrons find it harder to flow. The friction is the cause of the resistance in the circuit. Therefore, using this theory, by increasing the length of the constantan, the resistance should increase, as more collisions of the electrons and the atoms will take place. Equation Electric energy Kinetic energy Heat energy Prediction for Thickness Electricity in a wire is due to the flow of free electrons. The more of these that flow every second, then the greater the current. A resistance controls the current. The bigger the resistance then the smaller the current. In a previous experiment that I did, I found out that when two 10 ohme resistors are put parallel then the resistance is halved, this is because the resistance is inversely proportional to the thickness. I am basing my prediction on an analogy that I have been told. If you were at a football game and you were queuing up to get in at the turnstiles and there was only one turnstile open. It would take a long time to get through, but if you were to open another turnstile then it would take half the time to get in because some of the people have moved to the other turnstile. Picture of turnstiles So I am going to predict that when the thickness is increased then the resistance is halved. Fair Test To make this experiment a fair test, I did the following;   Made sure the circuit was in proper working order by putting a resistor in the circuit that I new the resistance of. I made sure the wire was cut exactly to the length required. I used the same wire, Constantan.   I changed the power, so I could take two readings in order to take an average. Results Length(cm) V1(volts) A1(amps) V1/A1(ohms) V2(volts) A2(amps) V2/A2(ohms) Average V/A(Ohms Length(cm) 170 150 130 110 90 70 50 30 Average V/A 37. 25 31. 405 27. 73 24. 98 19. 98 15. 53 11. 7 7. 29 Thickness(mm) V1(volts) A1(amps) V1/A1(ohms) V2(volts) A2(amps) V2/A2(ohms) Average V/A(Ohms 0Thickness(mm). 1/Thickness 5Conclusion for Length In the experiment for length, How does the Length of a wire affect the resistance, I found that my results show that the longer the wire is in length then the higher the resistance. Length graph Conclusion from Graph In my prediction, I stated that:   When the length of the conductor was increased, the electrical resistance will increase. The resistance was directly proportional to the length e. g. When the length is doubled, the resistance is doubled, and when the length is tripled, the resistance is tripled. These points are proven by this graph because it is a straight line which means that the resistance is directly proportional to length. Conclusion for Thickness In the experiment How does the thickness of a wire affect the resistance of a wire, I found that my results showed me that the resistance is affected by the thickness of a wire, when the wire has a bigger diameter then the resistance is much lower. Thickness graph Conclusion from Graph There was an unexpected result on this graph. I expected it to be a straight line so that the resistance was directly proportional to one divided by thickness. But as you can see it has come out as a curved line. Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.