W2 Assignment

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Electrical Engineering

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Jan 9, 2024

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Kaila Gough G00215407 Grantham University W2 Assignment 9/28/2023

Chapter 3 6. In a certain circuit, I = 5mA when V = 1V. Determine the current for each of the following voltages in the same circuit. A. V = 1.5V I = 7.5mA B. V= 2V I = 10 C. V = 3V I = 15 D. V = 4V I = 20 E. V = 10V I = 50 10. Determine the current in the circuit in Figure 3-23. a. R = 3.3k V = 5.0v I = 1.51mA b. R = 150 V = 7.5v I = 0.05mA c. R = 2.2M V = 500mV I = 227.27mA 12. If you wish to increase the amount of current in a resistor from 10 mA to 15 mA by changing the 20V source, by how many volts should you change the source? B. To what new value should you set it? C. what is the new value of the resistor? To increase resistor to increase the current through a resistor you can either increases the potential difference across the resistor by altering the variable resistor to increase the potential difference by 0.2V o raise the voltage while maintaining the resistance. Assuming your load is a resistor then your original load resistance was2.0 ohms. Therefore, if you want to increase the current to 15mA you’ll have to increase your voltage to 30V and your resistance would then remain the same. 16. For the bulb graphed in Figure 3-24, what is the resistance when the voltage is 25V? To find the resistance you would divide the Voltage by the current. In this case the voltage according to figure 3-24 is 25 and current is 0.25. So, 25/0.25 = 100. So 100mA is the resistance. 18.Determine the current in each case: In order to determine the current for each of these. You simply divide the voltage by the resistance. a. V = 9V, R = 2.7k ohms 9/2.7 = 3.33 mA b. V =5.5v, R = 10k ohms 5.5/10 = 0.55mA c. V = 40v, R = 68k ohms 40/68 = 0.588mA d. V = 1kV, R = 2.2k ohms 1kV / 2k ohms = 0.00045A

e. V = 66kV, R = 10M ohms 66kV / 10M = 6.6mA 22. A 5-band resistor is connected across a 12v source. Determine the current if the color code is orange, violet, yellow, gold, brown. The first band color Orange represents 3, 2 nd band color Violet represents 7, 3 rd band color yellow represents 4, and 4 th band color represents gold which is the multiplier of 0.1. Therefore, the resistance is 37 x 10^4 which equals 3.7k ohms 26 . The potentiometer connected as a rheostat in Figure 3-25 is used to control the current to a heating element. When the rheostat is adjusted to a value of 8 ohms or less, the heating element can burn out. What is the rated value of the fuse needed to protect the circuit if the voltage across the heating element at the point of maximum current is 100 V and the voltage across the rheostat is the difference between the heating element voltage and the source voltage? If we assume the resistance of the heating element is 10 ohms then the maximum current flowing through it would be : 100v/ 10ohms = 10A Therefore, a 10 amp fuse would be needed in order to protect the element from burning out. Section 3-3 Voltage Calculations 28. A small solar cell is connected to a 27k ohm resistor. In bright sunlight, the solar ccell looks like a current source that can supply 180uA to the resistor. What is the voltage across the resistor? In order to find the voltage you must multiply the current and the resistance together which would be 180 x 27 = 4.86V 32. Assign a voltage value to each source in the circuit of Figure 3-26 to obtain the indicated amounts of current. The resistor value in Figure 3-26(a) is 27k ohms and the current value is 3mA. In order to find the Voltage in the circuit using ohms Law V = R x I 27 x 3 = 81 Voltage = 81 Figure 3.26-1 Full Alternative Text (b) The resistance is equaled to 100m ohms and current is 5uA. In oreder to find the voltage using ohjms law the resistance and the current can be multiplied. 100 x 5 = 500V therefore the voltage drop across a 100M ohms resistor with a current of 5uA is 500V.

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c) The resistance value in the figure shown is 47 ohms and the current is shown as 2.5A. So ohms law states if you multiply the current and resistance you will have the voltage. So in that case 47ohm x 2.5A = 117.5volts. 36. Six volts is applied across a resistor. A current of 2mA is measured. What is the value of the resistor? According to Ohms law R = V/I So 6 / 2 = 3 Therefore, The resistance would be 3kohms. Ch 4. 6. Convert the following to kilowatts: In order to convert to kilowatts, we need to divide the number of watts by 1000 to find our answer because 1000W = 1kW. a. 1,000W = 1kW b. 3,750W = 3.75kW c. 160W = 0.16kW d. 50,000W = 50kW 8. Convert the following to milliwatts: In order to convert Watts to Milliwatts you need to multiply the number of Watts by 1000 this is because there are 1000mW= 1 Watt. a. 1W = 1000mW b. 0.4W = 400mW c. 0.002W = 2mW d. 0.0125W = 12.5mW 10. Convert the following to watts: a. 1.5kW = 1500W To convert kW to W. you must multiply by 1000 b. 0.5MW = 500,000W c. 350mW = 0.35W d. 9,000uW = 0.009W The power value 9000uW in words is “nine thousand uW(microwatt)”. 12. If a 300 W bulb is allowed to burn continuously for 30 days, how many kilowatt-hours of energy does is consume? To figure this out we must convert the power in watts to kilowatts by dividing by 1000. A 300-watt bulb has a power of 0.3kW. Next, we need to convert the time in days to hours by multiplying by 24. we can use the following formula: E(kWh) = P (kW) x t (hr)

If the bulb burns for 30 days continuously, that is equivalent to 720 hours. We can plug the numbers in the formula and get the answer: E(kWh) = 0.3kW x 720 hr E (kWh) = 216 kWh Therefore, 30 days continuous would consume 216 kilowatt-hours of energy. Section 4-2 Power in an Electric Circuit 18. If a resistor has 5.5V across it and 3mA through it, what is the power? Find the answer using this formula: P = V x I 5.5v x 3mA = 16.5miliivolts so the power is 0.0165 watts 20. What is the power when there is 500mA of current through a 4.7k ohm resistor? Ohms Law will help to solve this problem with the following formula to find the voltage of the circuit: V = I x R 0.5 x 4700 = 2350 Now you can use this formula to get the power value: P = V x I 2350 x 0.5 = 1175 Therefore, the power is equal to 1175 watts. 22. If there are 60V across a 680 ohm resistor, what is the power? To find the power of the resistor you can use the formula from ohms law: P = V x I In this case the V is = 60 volts and R = 680ohms. You can use I = V/R to calculate current through the resistor: 60/680 = 0.0882 amps Now you can use the other formula to get the value for the power 60 x 0.0882 = 5.292 Watts. 24. If a resistor is to carry 2 A of current and handle 100 W of Power, how many ohms must it be? Assume that the voltage can be adjusted to any required value? 25 ohms 28. A 6.8kohm resistor has burned out in a circuit. You must replace it with another resistor with the same resistance value. If the resistor carries 10mA, what should its power rating be? Assume that you have available resistors in all the standard power ratings. 68 x 0.01 = 0.68watts The power rating of the resistor is 0.68 watts. However, this is the minimum rating that you need for your resistor. It is better to choose a resistor with a higher power rating than the calculated value, to avoid overheating and damage. You can use a resistor with a power rating of 1 watt or more. 36. If a battery is rated at 650 mAh, how much average current will it provide for 48 h? C = I x t We need to rearrange the formula to solve for I