Prelab- DC 7

A-How temperature affects the conductivity of conductive metals and how it affects semiconductors.semiconductors B-What is superconductivity, how does it relate to temperature? Some examples of superconductors.superconductors.

1- A). Which of the following could be used as a discharge device in an inductive AC circuit? a) resistor b) diode c) metal oxide varistor d) "a" and "c", not "b" B. What is the purpose of a discharge device used in conjunction with opening a highly inductive circuit? a) to minimize the possibility of damage to the circuits insulation as a result of a high induced voltage b) to minimize the possibility of endangering the life of the person opening the controlling switch c) to allow the magnetic field to gradually collapse, thus limiting the value of the self-induced ernf d) all of the above C. The high voltage induced by an inductor when its circuit is opened could be used constructively for a) an automotive ignition system b) an electric fence c) both "a" and "b" d) neither "a" nor "b"

Notes on the verification of ohm's law by voltage method?

The effective voltage of alternating current is __________ times its highest or peak voltage. Select one: A. .9 B. .707 C. 100% D. E=IXR

Q1. a) An SCR based AC power controller circuit is given in Figure 1. The circuit connects a 240V 50Hz AC source vi to a resistive load with resistance of 100. If the delay angle is a-15°, draw the waveforms of the load voltage Vo, and the voltage across SCR2. Calculate the power supplied to the load. + Vi Va + 2 SCR2 H₁₁ SCR₁ Figure 1 SCR based AC power control circuit Va + 2 io b) Figure 2 is a single phase 2-level voltage source converter (VSC) with a DC voltage Vd-200V. A PWM scheme, by comparing a reference value with a 10kHz triangle waveform, is used to control the switches S₁ and S2. The modulation index of the PWM is m=0.8. With the aid of graphs explain how pulse signals for the switches are generated, sketch the output voltage Vo, determine the duty cycle, and calculate the average output voltage. + Vo + Vo √ ₂ == Figure 2 A single phase VSC

Refer to the circuit on the right. VEB = 0.7 V, when the BE junction is conducting. VECsat = 0.2 V B Vref = 2.2 V (Use two decimal places.) = ∞ VREF IL +5 V R LOAD Figure 2 a. What should be the value of R in ohms if IL is to be maintained at 146 mA under changing load conditions? b. In order to maintain this load current, what should be the maximum allowable load resistance in ohms?

The resistance of the copper filed winding of a dc machine at 20  is 0.2 ohms. After operating the resistance is found to be 0.23. Find the operating temperature. Where the temperature coefficient of copper at 20 deg. C   is 0.00386 /deg. C?

Nichrome ribbon resistor elements each has a resistance of 1 ohm. The element is made from sheet of nichrome alloy, 0.025 cm think. If the width of the ribbon is 0.3cm, what length is required per element in cm? Assume specific resistance of nichrome alloy to be 109microOhm-cm.

How about solving this using KCL equations? Thank you

The resistance of wire increases from 40 – ohm at 20 0C to 50 – ohm at 70 0C. Find the temperature coefficient of resistance at 0 0C.