Ohm S Law Lab

Electromechanical Technology Name(s): ______Basic Electronics Section: ______Ohms Law (30 pts.) Due Date: ______

Materials Required: Section 2: The effect of varying DMM resistance on current with voltage Power Supply constant Breadboard Misc. wires 9. Connect the circuit of Figure 2 with the Resistors: 100, 330, 470, power supply turned off. Begin with the 560, 820, 1 k first value of resistance in Table 3. Note this is the same basic circuit as section Procedure: 1. However, the ammeter is located in a different part of the circuit’s current path. Section 1: The effect of varying voltage on current with resistance constant 10. Measure the voltage applied to the circuit. Record the voltage in the 1. Measure the resistance value of all Measured Voltage column of Table 3. resistors. Record the value of each Caution, once you have set the voltage, resistor in Table 1. be careful not to adjust or bump any of the power supply knobs for the 2. Using your voltmeter, set the power remainder of section 2. supply for 1.5V. Record the measured value of voltage on the first line of Table 11. Refer to Table 3. Using the measured 2 under the heading Measured Voltage. values of voltage and resistance, calculate and record the current for each 3. Using Ohm’s law, calculate the current resistor. Record the calculated value in through the 100 resistor with 1.5 volts Table 3 under the heading Calculated applied. Note: Use your measured Current. value of resistance and voltage when calculating current. Record the value in 12. Turn on the power supply. Read the Table 2 under the heading Calculated value of measured current, and record Current. the results in Table 3.

4. Connect the circuit of Figure 1 with the 13. Turn the power supply off. Replace the power supply turned off. Be sure to resistor with the next value of resistance make sure the polarity of the equipment listed in Table 3. is correct. 14. Repeat steps 12 and 13 for all 5. Check your circuit connections by remaining values of resistance listed in tracing the path of electron flow. Table 3.

6. Apply power to the circuit. Verify the 15. Turn the power supply off. Disconnect measured value of current is close to the circuit. the calculated value of current. Record the measured value of current in Table 2 under the heading Measured Current.

7. Calculate the power dissipated by the 100 resistor. Indicate which formula you used.

8. Repeat steps 2-7 for each value of voltage listed in Table 2.

1 Section 3: The effect of varying Record the measured value of current resistance and voltage with the for Figure 3(b) in Table 4. current constant 21. Design a circuit that has the 16. Refer to the circuit schematic of Figure approximate value of current (10 %) as 3(a). Use Ohm’s Law to calculate the the circuits of Figure 3(a) and 3(b) but current in the circuit. Record the value with the following three restrictions: (1) in Table 4. voltage must be between 1 and 15 V; (2) resistance must be less than 1k; 17. Connect the circuit of Figure 3(a). and (3) the resistor must be a standard value available in your lab or from the 18. Measure the voltage and the current in parts room. the circuit. Record both values V and I in Table 4. 22. Draw the schematic for the circuit, showing the design values V, I, and R. 19. Connect the circuit of Figure 3(b) where Be sure to label all components carefully R=330 and the ammeter is connected and show the meter connections. Also, in the circuit. Calculate the value of show the design calculations (Ohm’s voltage required to maintain the same Law) you used and be sure to include amount of current in the circuit in Figure the calculated values of V, I, and R. 3(a). Record this value in Table 4. 23. Measure the resistor you have chosen 20. Carefully adjust the power supply and record the value in Table 5. voltage so that the current in the circuit in Figure 3(b) is approximately equal to 24. Connect the circuit. Measure the the current in the circuit in Figure 3(a). voltage across the resistor and the Record the value of voltage in Table 4. current in the circuit.

2 Table 1 Nominal Measured Resistance Resistance () () 1000 820 560 470 330 100

Table 2 Applied Voltage Measured Voltage Calculated Current Measured Current Calculated Power (V) (V) (mA) (mA) (mW) 1.5 V 2.5 V 3.5 V 4.5 V 6.0 V 7.0 V 8.0 V 9.0 V

Table 3 Measured Nominal Measured Calculated Current Measured Current Voltage (V) Resistance () Resistance () (mA) (mA) 1000 820 560 330 100

Table 4 Measured Measured Measured Calculated Calculated Circuit Value () Value (V) Value (I) Value (I) Value (V) a b

Table 5 Measured Value Measured Value Measured Value () (V) (I)