PHY 112L
Why is it important to use 2.00 V as the accepted value when calculating percent error in part 3 of the Electric Charges, Potentials, and Fields lab?
2.00 V is the midpoint for the voltage since the starting point it 4.00 V
The time constant t is the times it takes to discharge to _____% of its fully charged voltage, as well as the time to charge to ______% of its maximum voltage.
37% 63%
If the voltage in a circuit increases, but the resistance remains the same, then the current will a. increase b. decrease c. remain the same
A. Increase
What is the difference between AC and DC power supplies? Hint: think about what other types of power sources produce AC and DC power?
AC supply is constantly changing (alternating current) DC supply is steady, does not change (direct current)
Circle all of the physical quantities on which the Resistance of a material depends AND write the SI units next to all 5 quantities listed (a-e) below. a. length b. cross-sectional area c. current d. applied voltage e. resistivity f. all of the above g. none of the above
Answer: F a. meters b. m (squared) c. ampere d. watts e. ohm
What is the precise symbol of the multimeter mode you use to measure: AC current: ______ DC voltage: ______
A~ V---
How would the magnetic field strength B change if the solenoid used in lab were twice as long and the current through I was doubled, but it still only had 1340 total turns?
B is the same as magnetic field increases current increases as well
Dependent: _______ Independent: _______ Turns per unit length: _________
B=uonI ----> solenoid B B=uIn/2(I) ----> coil n=N/L
Give a brief definition of capacitance, its units, and the equation that governs capacitance below. As well as define all variables.
Capacitance is the ability to store charge. The equation that can be used is Q=CV, where Q is the charge on the capacitor, C is the capacitance and V is voltage
Parallel: ________ Series: _________
Cp= C1 + C2 Cs= C1C2/C1+C2
Give the name and SI units of the 3 physical quantities that can be measured with a multimeter.
Current (I)- Amps Voltage (V)- Watts Resistency (R)- Ω
Which physical quantities will be measured in the last section of today's lab; which are calculated? Measured: _________ Calculated: ________
Current and length Voltage and resistivity
Explain the two techniques used to measure the resistance in the first section of today's lab. Multimeter: _______ Ohm's Law: _______
Direct measurement R=V/I
What is the physical property responsible for chemical reactions and electrical phenomena?
Electrical charge
Briefly explain how to determine the RMS values of voltage (or current) signals using DataStudio in the Impendance lab
Find the peak values then divide by the square root of 2 for RMS Use Vrms=Vmax divded by square root of 2
Write both mathematical expressions and the units used in the lab for magnetic flux.
I=BAcostheta (weber) and I=A/N
What can be said about the total charge of a closed system if it is conserved?
If conserved, it will stay the same the entire time
Explain Len'z law.
Induced voltage opposes the direction of the magnetic flux
What is the difference between charging by conduction and charging by induction?
Induction is temporary and conduction is a permanent transfer
In an AC circuit with only a resistor, voltage and current are in phases. Give a brief physical description of what means for voltage and current signals to be in phase.
Maxima occurs simultaneously; peaks occur at the same time
Give the equation for the magnetic field generated inside of a solenoid; define factors
MonI where n= # of turns, I is current and Mo is 4Π*10^-7 Tm/A
Describe how to determine the relationship between the magnetic field of a bar magnet and the distance from the magnet in part1 of today's Magnetic Fields lab.
Move the magnet closer to the sensor and observe in its strength
Voltage: ________ and ___________ Current: ________ and ___________
Multimeter and less voltage Multlmeter and less current
Describe the connections needed to measure voltage and current in a circuit with a multimeter or any other device. Voltage:_________ Current: _________
Parallel Series
Electric field lines are always ________ to equipotential lines.
Perpendicular
If you are given two charged objects, one positively charged and one negatively charged, in which direction do the electric field lines always point?
Positive goes towards the negative
Charging: _______ Discharging: _______
Q= Qm (1+e- t/Rc) Q= Qoe- t/Rc
Write the formula for the amount of charge stored in a capacitor and define all variables.
Q=CV Q is capacitor C is capacitance V is voltage
Give the name and a brief description of the physical attribute used to determine the capacitance C of the discharging capacitor in today's lab.
Q=Qoe-t/Rc Q is capacitor Q not times e is the maximum amount of energy t/Rc is how much time since power supply is turned on
Write 2 equations for the equivalent resistance R(e) below. Series: _______ Parallel: ________
R=R1+R2 R= (R1R2)/(R1+R2)
What type of values for voltage (or current) must be used when applying Ohm's law to an AC circuit?
RMS values
Give the name a brief description of the procedure used to determine the direction of a magnetic field generated by an electric current, or vice versa?
Right hand rule, fingers curl in the direction of B.
Current: _______ Voltage: ________
Series Parallel
B: _________ A: _________ Theta: ___________
Strength of the magnetic field Area of wire loop Angle between B and A
Which 2 units are used for magnetic fields; what factor is needed to convert between them?
Tesla (T) and Gauss (G) 1 T= 10,000 G
Why is using the Pasco sensor to measure current or voltage better than using a multimeter?
The Pasco sensor saves data and you can view it later. The multimeter is constantly changing numbers and hard to keep up with
What happens to the magnetic field if the current that creates it is reversed?
The magnetic field will go into the page
Briefly explain how to determine the peak values for voltage (or current) using a multimeter in the Impedance lab.
The meter gives RMS values. You can the measurements with the multimeter (in RMS) and then multiply by the square root of 2.
To which port on the multimeter should the red probe be connected in order to measure voltage?
The red probe should be connected to the red indicator section which is labeled VΩ
How were the different current measurements compared in part 2 of last week's lab?
Using a percent difference calculation
Write down the equation for Faraday's law and explain
V=-N(delta I/delta t) The voltage is proportional to the rate of change of the magnetic flux of the number of loops (N).
Write the equations for Ohm's Law and Resistivity Ohm's Law: _______ Resistivity: _______
V=IR R=pL/A
Write down the equation for Ohm's Law and give name and units of each variable.
V=IR V is voltage I is current in amps R is resistance in Ω
Briefly explain the phase relation between a circuit's input current and the voltage across a capacitor Vc and Vl
Vl leads and Vc lags
Briefly explain the meaning of Vmax and Vrms and how they are related?
Vmax is maximum voltage Vrms is the voltage squared
V: ________ N: ___________ delta flux/ delta time: __________
Voltage # of turns Change of flux/ change of time
How are these values related to the peak or maximum values for voltage (or current)?
Vrms=Vmax/[2] Irms=Imax/[2]
What 2 conditions may be true of a magnetic field that is known to be inducing a voltage, and therefore a current, in a given wire configuration?
When the direction is zero degrees and has no strong magnetic field strength
Give the mathematical expressions for capacitive and inductive reactance below. a. Capacitance b. Inductive c. Physical effects
Xc=l/2ΠfC Xl=2Πfl resistance and inductance
Give the formulas for current (I) and impedance (Z)
Z=sqrroot(R2+ (Xl-Xc)2 I=v/2=v/sqrt(R2+ (Xl-Xc)2
How would you change R in the order to cut in half the time it takes an RC circuit to charge?
divide by 2
Clearly and concisely summarize the procedure for measuring capacitance C by using the voltage v. time graph of a charging capacitor in DataStudio.
divide the current by the slope
How would you change C in order to double the time it takes an RC circuit to discharge?
double it
The two symbols are used to describe the direction of the magnetic field. Which symbol represents the magnetic field going into the page and not.
out of the page in the page
What physical quantity is calculated and compared using a percent difference calculation in part 1 of the Resonance lab?
resistance
Clearly and concisely summarize the procedure for measuring the time constant t using the voltage v. time graph of a discharging capacitor in DataStudio.
t=t37-to
