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# GCSE: Electricity and Magnetism

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Meet our team of inspirational teachers Get help from 80+ teachers and hundreds of thousands of student written documents • Marked by Teachers essays 19
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1.  ## Ohm's Law coursework

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at a constant temperature is proportional to the potential difference (voltage). Therefore V � I is constant. This means that the resistance of a metallic conductor is constant providing that the temperature also remains constant. Furthermore, the resistance of a metal increases as its temperature increases. This is because at higher temperatures, the particles of the conductor are moving around more quickly, thus increasing the likelihood of collisions with the free electrons. The variables in this investigation are: - The length of the wire - The cross-sectional area of the wire - The material of the wire - The temperature of the wire Input: * The length of wire.

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2.  ## Resistivity Coursework

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Constants are current (I), cross sectional area of wire (A) Resistivity (?) and temperature of the Nichrome wire. An R against L graph must look like this, (look below,) if resistance and length are directly proportional to each other. A4c: Detailed Plan * confirm power supply unit is at 0v * construct apparatus as illustrated in diagram * connect voltmeter negative crocodile clip on 0.100m * increase current to 0.30A * take reading from voltmeter as quickly as possible for the wire to remain at the same * switch off power when entering the reading into required data * connect the voltmeter negative crocodile clip to increased 0.200m * repeat process till I reach 1.000m * repeat the whole process again but with 0.60A * plot a graph of R vs.

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3.  ## Draw stress and strain graphs for the metal copper and the alloy constantan. Calculate the figures of young's modulus for copper and constantan. Discuss the physics involved.

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I have included a diagram of the set-up (Figure 1) below which was used to obtain the results I was given. Figure 1 (SOURCE: AS PHYSICS CDROM) The experiment works by a G-Clamp holding the wooden block steady, this will place pressure on the wire to keep it steady at the clamped end. The cardboard bridges keep the wire straight and in place throughout its length. The pulley allows the wire to move freely along it to keep friction minimum. As load is increased this puts pressure on wire and it may extend in length, which is the variable I will be measuring.

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4.  ## Investigation into Energy Released From Burning Various Alcohols.

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The time left for the alcohol to burn will also affect the results, as the longer it is left to burn, the more energy will be released. Finally, the height of the water above the flame will affect the results. As the energy is released, some of it will be dispersed into the air before reaching the water. With a larger distance between the water and the spirit burner, there would be more time for the energy to disperse, and the amount of energy in the water would be lower than if the water was closer to the spirit burner.

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5.  ## Thermal insulators.

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Which means that I need something that is a bad thermal conductor (good thermal insulator) to keep the amount of conduction to a bare minimum? Plan I am planning to test five materials (paper, cling film, cloth, bubble wrap and plastic) and one control, three times and find the average (to ensure accuracy). Whichever material changes the temp of the water the least is the best insulator. I will wrap them around a 200ml beaker (no lid) and fill it with 200ml of boiling water.

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6.  ## Investigate young's modulus behind Constantan and Copper.

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By using this program, I will be able to achieve very precise results. Method: I will firstly collect the various equipment I will need which includes: A G clamp, wooden blocks, pulley, mass hangers with slotted weights, copper and constantan wire samples and a ruler. I will measure using a micrometer, the diameter of the wires and the length with a meter ruler. I will measure the length of the wires in metres and measure off very accurately to one decimal place.

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7.  ## The factors affecting the resistance of a metalic conductor.

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V I V = IR R= V/ I V= Potential difference in volts (V) I = Current in amps (A) R= Resistance in a unit is called an ohm () The graph below shows the relation between the current and the voltage of a conductor, showing that as the current increases the voltage increases. This is what is termed as Ohm's Law. In order to find the resistance of a conductor, the gradient of the graph is found out using the formula: Gradient of the graph = I/V Whereby R = 1/gradient FACTORS AFFECTING THE RESISTANCE OF A WIRE: There are four external factors that influence the resistance in a conductor.

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8.  ## Investigation into the Physics of a Light Dependent Resistor.

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According to Ohm's law, the resistance falls in the LDR as the current throughout the circuit increases. The reason for this increase in current is due to the greater number of charge carriers in the semi-conductor inside the resistor. In this case, the charge carriers are electrons. This increased number of electrons when light intensity increases, raises the semi-conductor's Conductivity and therefore lowers its Resistivity as the two values are inversely proportional. It is only reasonable to say that as the current through the circuit increases, so too will the voltage across the LDR. A Quantum Explanation for the behaviour of an LDR I have already said that the increased voltage across an LDR is due to

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9.  ## Factors Affecting The Resistance Of A Metal Wire.

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Preliminary Work 4. Copper wire - 0.247mm diameter Length Current (A) Voltage (V) Resistance (?) 10cm 0.400 0.150 0.375 60cm 0.370 0.100 0.270 Nichrome wire - 0.247mm diameter Length Current (A) Voltage (V) Resistance (?) 10cm 0.300 0.630 2.100 60cm 0.190 1.130 5.947 Nichrome wire - 0.457mm diameter Length Current (A) Voltage (V) Resistance (?) 10cm 0.380 0.140 0.395 60cm 0.290 0.600 2.000 From the results, it can be seen that the nichrome wire with a diameter of 0.247mm had the greatest variation within the results, so this wire will be used.

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10.  ## To investigate how the resistance, R, of a length of wire, l, changes with diameter, D and determine the resistivity of the material the wire used.

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The length is also an issue as the longer the wire the higher the resistance because the electrons have to travel past more atoms and collisions between the electrons and the atoms are more likely then in shorter wires. Resistance should also be proportional to the length of the wires. So, I have decided on using a length of 1m. In a metal, conduction electrons are free to move the fixed positive ions, when a voltage is applied i.e. a battery source; the free electrons are repelled by the negative terminal and attracted to the positive one.

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11.  ## An Investigation To See How Resistance Can Be Changed By Variables.

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Current- this will be kept low so will not become hot, and effect resistance. A set value will be decided. Temperature-the higher the temperature the wire is at the more resistant it becomes and will be cheap low enough not to let the temperature increase. Equtions; R = V I Resistance is equal to Voltage/Current R L C.S.A Circuit; Outline Plan; * The variable I will be changing is "length of Constanton wire." * I will find the length in a pre-test. I will also combine the to together to find out the range of length with the wire type.

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12.  ## Investigating how the length of wire affects its resistance

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Because the wire is longer, the chances of the electrons colliding with each other also increases, so this causes obstruction and resistance will increase. In this case, there will be different lengths of the wire measured, and the longest wire will have the highest resistance. (With the width kept the same). With more atoms, the more likely the moving electrons will collide with them, and so the flow would be less meaning a higher resistance. With more length, the chances of the neighbouring electrons colliding with each other should also increase.

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13.  ## Experimental Verification of Ohm's Law

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* Ammeters and Voltmeters have terminals marked + and - which must be connected correctly to the battery. Only close the switch when you are sure that you have wired the circuit properly. * Close the switch and smoothly adjust the rheostat from minimum resistance to maximum resistance and at regular intervals note the meter reading and hence obtain a set of values from the two meters (at least 6). * Divide the Voltage by the current to get Resistance and tabulate the results in a table as shown below Current, I (A) Voltage, V (V) Voltage/Current , R (?)

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14.  ## Resistance Aim: my main aim is to investigate the factors that affect the resistance in a conductor, in which here I am using a nichrome wire.

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What we know about current already is that it is nothing but the rate of flow; however when the temperature rises the atoms also vibrate in their own balance more forcefully impending the flow of electric charges due to more frequent collisions. More electrons are available to conduct the current in the wire. Collision with lattice ions is less frequent. The current increases and the resistance decreases. However, the cross-section area will also have an effect, as the larger this is, the more charge can pass through it at the same time as it passes through a given length.

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15.  ## An investigation into the efficiency of an immersion heater 2

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I will use the following formula to calculate the immersion heater's efficiency. Energy supplied 100% Energy produced Method: Circuit diagram The apparatus and circuit were set up and arranged as shown in my diagrams above The measurements I will take are as follows: * initial temperature of water * amps after 2 minutes * volts after 2 minutes * temperature of water after 2 minutes To get a fair and average result I will change the type of wire I

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16.  ## Investigating the young modulus of a wire

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This is called strain. Strain is the amount of deformation a material experiences per unit of original length in response to stress. Change in length x Original Length L The same definition and symbols are also used for tensile and compressive stress. As strain is a ratio of two lengths, it has no units and is therefore dimensionless. When stress is applied to a material, strain is produced in the material. The strain is proportional to the stress provided the stress does not exceed a limit known simply as the limit of proportionality.

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17.  ## In this coursework, I will be analyzing and proving that although metallic conductors are good conductors of electricity, they are affected by resistance.

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Thus all metals are good conductors of electricity. But some metals have more free electrons, so they are better conductors, since more electricity can be passed. EXISTENCE AND MOVEMENT We now come to our next question, 'How does a wire conduct electricity?' We all know now that the there are free electrons in any piece of metal, but it still can't conduct electricity, if we just leave it by it self. This is because; there is no potential difference. If we examine a piece of metal closely, it turns out that the free electrons form a cloud, or a sea of electrons.

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18.  ## An Investigation Into The Resistance Of Conductive Putty

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I will need the light bulb to show if the circuit is complete. The battery pack is control the electrical currant and the crocodile clip and wire to carry the currant. Safety The first danger is the power of the electrical currant. To prevent any danger of electrical shocks I will use the battery pack to control the strength of the currant and turn it down to four cells.

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19.  ## How does the power dissipated by a light bulb vary with voltage?

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Graphs This is what I think my two graphs will look like: P/W P/W Voltage/V Voltage2/V2 1. The first graph will look like this because as the voltage increases, the current also increases. As they both increase, the power increases by a greater amount each time so the graph will have a curved line. 2. The second graph will look like this because as the power and voltage2 are proportional. This is shown by the equation P = V2/R. If the resistance of the light bulb remains constant, power and voltage2 increase proportionally.

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20.  ## Investigation in resistance in wires

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This will give me a larger group of data than if I just increased one of them. I will need to use the preliminary tests to work out the gaps I will be increasing them by. Hypothesis I predict that, the length of the wire will be proportional to the resistance; therefore if the length of wire gets longer the resistance will get greater. My prediction is that the shorter the wire the higher current will be and the longer the wire the lower the current will be at each voltage section.

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21.  ## Resistance of a Wire

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Material of wire - wires of different densities will block more or less electrons Temperature - the vibration of warm molecules makes them more likely to collide with electrons, and resistance increases with temperature. Variables Independent- length Dependent - Voltage, current to measure, resistance Controlled - Temperature, material of wire, cross sectional area Circuit diagram Method 1. set up apparatus as shown above 2. measure out a 1m length piece of wire and connect it to the crocodile clips 3. close the switch 4. set the variable resistor so that you get a less biased result- below 0.5 amps 5.

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22.  ## Aim: The aim of this experiment is to see how the length of a nichrome wire affects its resistance.

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If there are more collisions that means there is more resistance. Example: If there are 10 free electrons and have to go through 2 wires: a)10 cm and b)20 cm, there will be more resistance in wire b) as there will be more molecules in the electron's path in wire b) than in wire a). Aim: The aim of this experiment is to see how the length of a nichrome wire affects its resistance. Hypothesis: Resistance is caused by the collision of free electrons the fixed particles of the metal and its impurities therefore if the length of the wire is doubled; the electrons collide with twice as many molecules thereby doubling the resistance.

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23.  ## Resistance of a wire

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TRIAL 1 Length (cm) Voltage (V) Current (A) Resistance (?) 100 6,4 7,2 0,888888889 90 6,3 7,7 0,818181818 80 6,2 8,7 0,712643678 70 6,3 10,2 0,617647059 60 6,1 11,5 0,530434783 50 6,1 13,7 0,445255474 40 6,15 16,8 0,366071429 30 5,83 21,8 0,267431193 20 5,71 29,3 0,194880546 TRIAL 2 Length (cm) Voltage (V) Current (A) Resistance (?) 100 6,4 7,3 0,876712329 90 6,4 8,1 0,790123457 80 6,67 9 0,741111111 70 6,28 9,9 0,634343434 60 6,32 11,9 0,531092437 50 6,28 14,2 0,442253521 40 6,12 17,3 0,353757225 30 6,09 22,4 0,271875 20 5,9 32,9 0,179331307 TRIAL 3 Length (cm)

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24.  ## What factors affect the resistance of Ni-Chrome wire?

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This was also show within my preliminary results as increased the amount of filament bulbs (in affect increasing the amount of wire) the resistance increased. Resistance: x = length of wire x = R = V/0.25 0.25 = Amps 2x = 2R = 2V/0.25 V = Volts 3x = 3R = 3V/0.25 R = resistance 4x = 4R = 4V/0.25 As you can see I think that as you double the length of wire the resistance also doubles, because of this the voltage must double as it is being divided by a constant and it must double so the resistance can double.

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25.  ## Resistance of a Wire

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Results Plan The heading for my results table will be 'dial voltage', 'actual voltage', 'length of wire', 'current', and 'resistance'. To ensure a fair test I will make sure that the dependent variable will be the same through out the experiment. Safety I will assure that when I conduct my experiment, I will have a clear space between me and other students. I will use a heat proof mat to be the base of the wires so it will not heat up.

• Word count: 1183