Of A Wire Essay, Research Paper
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 OHMResistance is defined by: R= V/I????????????????? ????????????????????????????????????????????????????????????????????????????????????????????????????????? If
I= 2A when V= 12v, then R= 12/2?? =????? 6 ΩRESISTORSSome
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= V1 + V2 + V3????????????????????????????????????????????? V1= IR 1 ??????????????????????????????????????????????????????????????????????? V2=
IR 2 ??????????????????????????????????????????????????????????????????????? V3=
IR 3 If R is the
combined resistance, V= IR So: IR= IR1 + IR2 + IR 3 Dividing both sides by I R= R1 + R2 + R3 ??????????????????????????????????????????????????????????????? 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 3But:I
1 = V/R1 ??????? I
2= V/R2 ??????? I 3= V/R3Also, if R is the combined Resistance, V=IR. So:V/R = V/R1 + V/R2 + V/R3 Dividing
both sides by V: 1/R = 1/R1 + 1/R2 + 1/R3 Tow
resistors in Parallel: 1/R = 1/R1 + 1/R2 = R2/R1R2 + R1/
R1R2 Therefore: ????? 1/R= R2+R1/R1R2Inverting
both sides:R=
R1R2/R1+R2 = product of resistances/sum of resistancesWAYS 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
? ∝? Length ??? This is because the wire acts like
a series of resistors, whci restrict the flow of electricity. Therefore, the
longer the wire, the more the electricity is restricted over the distance. APPARATUS ????? PLAN1. I
will measure the resistance of 8 different lengths of nickel-chrome wire using
the ammeter-voltmeter method. 2. For
the f
the wire and then I will measure the voltage across the 10cm 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 10cm to
80cm. 5. I
will repeat the whole process to prevent any errors. I will take all the
readings again staring this time at 80cm 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) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 First Voltage (V) First Current (A) First Resistance (Ω) Second Voltage (V) Second Current (A) Second Resistance (Ω) Average Resistance (Ω) Ohm-meter Reading (Ω) 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
(Ω) ??????????????????????????????????????????????? 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 4V. 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 10cm to 80cm 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 80cm mark
and working my way back to 10cm in steps of 10cm. 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: ???????