08-16-2017, 09:29 PM
What we will do today o Creation of lemons o find out more about the internal resistance of the batteries o know what the electromotive force is o use an oscilloscope to measure the frequency and the voltage from a signal generator 3. Use of lemons, limes and potatoes to feed a copper zinc LED 4. make batteries there is nothing special about batteries - but these have a high internal resistance. R l think you the best way to minimize the internal
3. the resistance of your battery? Think of the resistivity (lemon is a poor conductor) 5. Battery what is the main energy transfer in a battery? Power this is powered by two 1.5 V AA batteries in series - what is the supply voltage? What is the EMF of the offer? After some time the battery should be replaced; Why? That is what determines the speed with which he runs down? That is what determines the amount of current is drawn from the power supply? 6. EMF electromotive Force EMF is the external labour expended by charging unit to produce a difference in electrical potential between two terminals open circuit o this is the same definition that the voltage, but on an open circuit (no power) o why is - this important definition?
4 7. Batteries have internal resistance circuit has now two resistors internal resistance of the battery, r is very low. R is much more the total resistance of the circuit is total R = R + r I = E / (R + r) 8. Batteries have internal resistance is responsible for the lap of the circuit, the sum of the GEF must be equal to the sum of the voltage leading to EMF = drops IR + I r the Terminal voltage is equal to IR if this can be rearranged to give: V = E - I r and interpreted as Terminal voltage = GEF - "lost volts 9. R small total R = r + R - SMALL current will now be greater that the total resistance of the circuit is much lower pressure lost across r V = I (large) r lost voltage will now be a problem so a small resistance of connected load is a battery is seen in a starter on a car engine
5 10. The starter on a conventional car motor projectors are connected in parallel to the terminals of a 12 volt battery. The motor starter is also controlled by the ignition in parallel. Since the starter motor has a very low resistance, it requires a very high current (for example 60 (A)). The battery itself has a low internal resistance (say 0.01 ). Emerge projectors lamp R Starter ignition 12V power much lower (they have a higher resistance) what will happen to light? 11. Use of high internal resistance 12. Quick questions o. 1. A 9.0 volt battery has an internal resistance of 12.0 o (a) what is the potential difference between its terminals when it provides a current of 50.0 my?
6 o what is the maximum current the battery could provide? o draw a sketch graph to show how the terminal potential difference varies with the power supply if the internal resistance remains constant. The way in which the internal resistance can be obtained from the graph? o and the current increases to 60 mA. What is EMF and internal resistance of the cell? . when the carrier increases the volume, resistance is changed to 100 2. A cell of a deaf aid provides a current of 25.0 my through a resistor of 400 V = E - I r V = IR E = I (R + r) you need to set up a simultaneous equation 13. E = 10 + (25 x 10-3 x 114.3) = 12.86 VIV Answers 1. (a) pd = E - I r = 9 - (50 x 10-3 x 12) = 8.4 V (b) current max = E / R = 9 / 12 = 0.75 A 2. E = I (R + r) E = 25 x 10-3 (400 + r) and E = 60 x 10-3
7. (100 + r) so, 25 x 10-3 (400 + r) = 60 x 10-3 (100 + r) then r = 114.3 14. Oscilloscope use the signal generator to create A / C (AC) on the oscilloscope Piochez 2 signals from 2 different frequencies train frequency of the oscilloscope add the magnitude of the wave height how do you use an oscilloscope as a DC and AC voltmeter? How do you use to measure frequency? 15. Voltage what value average voltage or alternating current is greater than an integer number of cycles? power is calculated by P = IV, me and the V sign together, therefore the power change is always positive 16. positive power calling the maximum value of I p V p and a minimum of zero 0V P = I p V p average power = I p V p P = 1/2 I p V p = 1/2 I p 2 R = 1/2 V 2 p / R (using V = IR)
8 17. voltage RMS (root average car)