Chapter 2
Resistive Circuits

m2.4 Wye-Delta Transformation

Find (a) the currents I₁ and I₂ in the circuit of Fig. m2.4 and (b) the power delivered by each of the two voltage sources. Use these component values: V ₁ = 15 V, V ₂ = 15 V, R₁ = 3.3 kΩ, R₂ = 1.5 kΩ, R₃ = 4.7 kΩ, R₄ = 5.6 kΩ, R₅ = 1.0 kΩ, and R₆ = 2.2 kΩ.

NI Multisim Measurements

Enter the circuit of Figure m2.4 into NI Multisim. Use measurement probes to measure each current, and use the wattmeter to measure the power associated with each voltage source.

• Place components from the “Virtual Components” palette.
• Place a ground symbol and attach it to the negative terminal of the voltage source.
• Place a Simulate → Instruments → Measurement Probe for each current.
• Place a Simulate → Instruments → Wattmeter for each voltage source, taking care to wire the wattmeters according to the passive sign convention.

NI myDAQ Measurements

Build the circuit of Figure m2.4. Use the myDAQ DMM (digital multimeter) as an ammeter to measure each of the two currents; use the DMM as a voltmeter to measure each of the two voltage source values.

• Measure and record the resistance of each resistor individually; do this before you connect the resistors together.
• Place the resistors to match the resistor orientations shown in Figure m2.4.
• Use the myDAQ -15V power supply connection for the left voltage source and the +15V power supply connection for the right voltage source; connect AGND (Analog Ground) to the node identified by the ground symbol.
• Measure the actual values of V ₁ and V ₂ when connected to the circuit; expect them to be slightly less than 15 volts.
• Remember to insert the DMM ammeter in series between the voltage source and the resistor.
• Determine power as the product of measured voltage and measured current.