Electricity and Light Pre Lab Questions The pre lab questions can be answered by reading the theory and procedure for the related lab. You are strongly encouraged to answers these questions on your own. Each question is worth 1 point towards the lab grade for the unit. The questions are designed to give you some insight into the lab and to address known areas of difficulty. The questions will be turned in prior to the start of the lab. Some of the subject matter address in these questions can be on the lab final.
UNIT 15 Introduction to laboratory test equipment 1) What measurements is the Digital multi-meter capable of measuring? See Appendix II. 2) Voltages are measured with an element and currents are measured in with the element. 3) When measuring a voltage or current and the voltmeter reading indicates a 1 followed by blank spaces what must be done to obtain a measurement? See Appendix II 4) What kind of measurements is primarily made with an oscilloscope? 5) When making a time base measurement, which scale (horizontal or vertical) is used for time and which for voltage. Also indicate which knob on the oscilloscope controls these measurement settings? See appendix I.
UNIT 16 Electric Fields: 1) What is an electric field? 2) What are the units for an electric field. List both of them. 3) What is an equipotential line? 4) Lines of force originate on charges and terminate on charges. 5) Electric field lines are (parallel, perpendicular) to equipotential lines.
UNIT 17 Capacitance 1) As a capacitor is discharged through a resistor the area under the curve of current (I) vs. time (t) will yield what? 2) The unit for capacitance is called a and it is designated by what letter. 3) A graph of charge(q) vs. volts (v) should yield a linear line with the slope representing what quantity? 4) Identify and write the equation for the two circuits shown below to determine the total equivalent capacitance. C A C B C C C A C B C C Type of circuit 5) Determine an equation to find the equivalent capacitance for the circuit on the right by combining the equations above. C A C B C C
UNIT 18 DC Circuits Please see corrections to the lab manual for this unit at the end of this file. From Figure 18-5 1) The three resistor that make up R 3 as shown in figure 18-5 is an example of resistors connected in and their equivalent resistance is ohms 2) In Figure 18-5 the resistor R 1 and R 2 connected between points B to D is an example of resistor connected in and the equivalent resistance between points B and D is 3) A shorted resistor would have a value of ohms and an open resistor a value of ohms 4) What are the current junction and voltage loop equations for the circuit in Figure 18-3? 5) Solve for I 1, I 2 and I 3 using Kirchoff s rules for figure 18-5 with the given resistor values. (You will be using simultaneous equations and substitution). V 1 =V 2 = 3 volts. Note: Check the help file for unit 18 available on the lab website.
UNIT 19 Potentiometer 1) A potentiometer measures the of a cell. 2) From equation [1] if the internal resistance, r, and emf, E, is constant, as more current, I, is drawn from the cell what will happen to the terminal voltage, V T. 3) From procedure Part B when an external resistance R L, loads an EMF source and when R L is equal to the internal resistance of the cell, r, (i.e. R L = r). What is the terminal voltage, V T, in terms of the emf source, E? 4) Write an equation to determine the terminal voltage of a cell, V T using the terms L std, L T and E std.
UNIT 20 Responses of Passive Circuit Elements 1) AC current through a perfect inductor or capacitor is out of phase with the AC voltage across the inductor or capacitor. 2) What is reactance? What is impedance? What are their units? 3) What is the name for the units of an inductor and capacitor and the symbols which represent them? 4) For an inductor the current and voltage is out of phase by an angle φ. How can this angle be determined theoretically? 5) What are the equations for the time constants, τ, for an RL and RC circuit?
UNIT 21 AC Circuits 1) When a circuit containing an inductor, resistor and capacitor is at resonance the phase angle between current and voltage is degrees? 2) At resonance what is the relationship between inductive and capacitive reactance? 3) What formula would you use to determine the impedance of a circuit containing a resistor, capacitor and an inductor at any given frequency? 4) When an ideal capacitor, inductor and resistor are connected in series what equation is used to determine the phase angle between the AC voltage and current? 5) From the procedure for this experiment, what should be done to the input voltage each time the frequency is changed?
UNIT 22 Reflection and Refraction 1) What does each term represent in equation [1]. 2) What does the term Normal mean in the context of dealing with an optical surface? 3) Describe how light behaves in relation to the Normal when traveling between two interfaces in the following cases: from a less dense medium to a denser medium from a denser medium to a less dense medium 4) A convex lens is also known as a (converging, diverging) lens and a concave lens is known as a (converging, diverging) lens. 5) Describe where the focal points are for a convex and concave lens are located.
UNIT 23 Diffraction and Interference Please see corrections to the lab manual for this unit at the end of this file. 1) What happens when light encounters an opaque barrier with a narrow slit opening? 2) What is diffraction? 3) Light has a nature. 4) Circle the appropriate answers. For a single slit, measurements are made from a diffraction pattern between the slit and the pattern and between the central peak and each subsequent (bright, dark) band. These measurements along with the order and wavelength can be used to determine the (width, spacing) of the slit. 5) Circle the appropriate answers. For a double slit, distance measurements are made from an interference pattern between the slit and the pattern and between the central peak and each subsequent (bright, dark) band. These measurements along with the order and wavelength can be used to determine the (width, spacing) of the slit.
Unit 18 This schematic better represents the wiring within the circuit box. Procedure step 6 is rewritten to better explain the need to add R F. Figure 18-5 6. Use the voltages V 1 =V 2 = 3 Volts, and the given resistances for R 1 and R 2. The digital multi-meter, DMM, has an internal resistance, R F = 8Ω, which contributes to the resistance in the circuit when measuring the current. When current is being measure the DMM is in only one loop at a time. To account for this resistance during calculations for the currents add the 8Ω to R 3, it is the resistance common to each loop when making the measurements. Determine the Theoretical currents for I 1, I 2 and I 3 using Kirchhoff s rules. Unit 24 In the data table on page 135. Slit spacing, d, is determine using the Position of bright spots. Slit Width, a, is determined using the Position of the Dark bands