Example research essay topic: Power Supply R R - 1,665 words

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Investigating The Factors Which Affect The Resistance Investigating The Factors Which Affect The Resistance Of A Wire Background KnowledgeRESISTANCEElectrons move more easily through some conductors when a potential difference is applied. Resistance is determined by how good or bad a conductor a material is. A good conductor has a low resistance while a poor conductor has a high resistance. THE OHM Resistance is defined by: R = V/I? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? If I = 2 A when V = 12 v, then R = 12 / 2? ? = ? ? ? ? ? 6 &# 937; RESISTORS Some conductors are made from carbon or alloy wires, and are intended to have resistance, so we call them resistors.

Resistors used in everyday life have values ranging form usually a few ohms, but go up to millions of ohms. A Resistor: ? RESISTORS IN SERIES The resistors below are in Series. The current flowing through all (I) is the same, and the separate potential difference across then is the same as the total potential difference across the 3 (V). i. e. ? ? ? ?

V = V 1 + V 2 + V 3? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? V 1 = IR 1? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? V 2 = IR 2? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? V 3 = IR 3 If R is the combined resistance, V = IR So: IR = IR 1 + IR 2 + IR 3 Dividing both sides by I R = R 1 + R 2 + R 3? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? RESISTORS IN PARALLEL The resistors below are parallel. The total current (I) equals the sum of the currents in the separate branches, and the potential difference between the ends of each is the same.

i. e. ? ? I = I 1 + I 2 + I 3 But: I 1 = V/R 1? ? ? ? ? ? ? I 2 = V/R 2? ? ? ? ? ? ? I 3 = V/R 3 Also, if R is the combined Resistance, V = IR.

So: V/R = V/R 1 + V/R 2 + V/R 3 Dividing both sides by V: 1 /R = 1 /R 1 + 1 /R 2 + 1 /R 3 Tow resistors in Parallel: 1 /R = 1 /R 1 + 1 /R 2 = R 2 /Therefore: ? ? ? ? ? 1 /R = R 2 +R 1 /R 1 R 2 Inverting both sides: R = R 1 R 2 /R 1 +R 2 = product of resistances / sum of resistances WAYS OF MEASURING RESISTANCE 1. AMMETER-VOLTMETER METHOD 2. USING A MULTIMETER TO MEASURE RESISATNCE FACTORS AFFECTING THE RESISTANCE 1. TEMPERATURE OF THE WIRE At low temperatures, the atoms in the wire vibrate less, so it easier for the electrons to pass through because of the low resistance. At high temperatures, the atoms vibrate more, offering more resistance and making it harder for the electrons to pass through. PREDICTION I predict that the longer the wire, the higher the resistance. ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

i. e. ? ? ? ? ? ? ? ? ? ? Resistance? &# 8733; ? Length? ? ? This is because the wire acts like a series of resistors, what restrict the flow of electricity.

Therefore, the longer the wire, the more the electricity is restricted over the distance. APPARATUS? ? ? ? ? PLAN 1. I will measure the resistance of 8 different lengths of nickel-chrome wire using the ammeter-voltmeter method. 2. For the first length, which will be 10 cm, I will measure the current going through the wire and then I will measure the voltage across the 10 cm of wire. 3.

I will then find the resistance of the wire using Ohm? s Law, where I will have to divide the obtained voltage by the current reading to get the resistance. 4. I will repeat the above process for all the lengths of wire, ranging from 10 cm to 80 cm. 5. I will repeat the whole process to prevent any errors.

I will take all the readings again staring this time at 80 cm and working my way back. 6. Because I will have two measurements for the resistance of each length of wire, I will find the average of these two readings. 7. I will record all the results in a table like the one below. 8. I will use a multimeter as an Ohmmeter just to check the resistance in case of any miscalculation. Length (m First Voltage (V) First Current (A) First Resistance (&# 937; ) Second Voltage (V) Second Current (A) Second Resistance (&# 937; ) Average Resistance (&# 937; ) Ohm-meter Reading (&# 937; ) SAFETY I will ensure that none of the wires are frayed and that there is no water near any electric equipment; as in all electrical experiments. HANDLING RESULTS I will draw a graph of Resistance against Length of wire with Resistance on the Y-axis and Length on the X-axis.

Resistance (&# 937; )? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? If my prediction is right, ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? The graph should show a? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Straight line through the origin. ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

Length (m) AT THIS POINT IN MY INVESTIGATION I CARRIED OUT THE EXPERIMENT METHOD 1. I set up the equipment as shown below. 2. I connected the multimeter in series with a D. C.

power supply, setting the value to 4 V. The multimeter was better to use because of the larger currents and because the readings are given to 2 decimal places. 3. I connected a one metre length of nickel-chrome wire which was taped a metre ruler to he output from the ammeter. 4. I then connected the voltmeter across the wire I was testing. 5.

I connected the negative terminal of the voltmeter to the negative terminal of the power supply, therefore completing the circuit. 6. 10 cm of wire were stepped off by the voltmeter leads and I recorded the readings of voltage and current. 7. I repeated the above process from 10 cm to 80 cm in steps of 10 8. Because the shorter lengths of wire became quite hot, the readings were taken quickly, but I allowed the wire to cool down before the next reading. 9. I repeated the whole experiment again, this time starting off at the 80 cm mark and working my way back to 10 cm in steps of 10 cm. 10. I then checked my readings with the multimeter we used in the experiment as an Ohmmeter.

I recorded the resistances for each length of wire after the wire had been disconnected from the circuit. APPARATUS USED: ? ? ? ? ? ? ?

Research essay sample on Power Supply R R