Circuit Lab B/C

[azboy1910]

Let's get this marathon started!

1. What is the capacitance of two parallel plates which are 5.3 mm apart, have an area of 30.4 mm^2 each, and have a dielectric constant of air between them (k = 1.0006)?
2. Three light bulbs are in series and connected to a battery. One of the light bulbs is disconnected. What will happen to the other bulbs?
3. A proton is moving east towards a magnetic field pointing upwards. What is the direction of the force exerted on the proton?

[Krish2007]

Let's get this marathon started!

1. What is the capacitance of two parallel plates which are 5.3 mm apart, have an area of 30.4 mm^2 each, and have a dielectric constant of air between them (k = 1.0006)?
2. Three light bulbs are in series and connected to a battery. One of the light bulbs is disconnected. What will happen to the other bulbs?
3. A proton is moving east towards a magnetic field pointing upwards. What is the direction of the force exerted on the proton?

1) 5.079 * 10^-11
2) All 3 light bulbs will turn off since it is an open circuit
3) North or upwards

[azboy1910]

Let's get this marathon started!

1. What is the capacitance of two parallel plates which are 5.3 mm apart, have an area of 30.4 mm^2 each, and have a dielectric constant of air between them (k = 1.0006)?
2. Three light bulbs are in series and connected to a battery. One of the light bulbs is disconnected. What will happen to the other bulbs?
3. A proton is moving east towards a magnetic field pointing upwards. What is the direction of the force exerted on the proton?

1) 5.079 * 10^-11
2) All 3 light bulbs will turn off since it is an open circuit
3) North or upwards

Click to Show Answer

1. Make sure to give units next time in your answer. Also, make sure to round your answer to the least number of significant figures, which is two in this question (in 5.3 mm).

For this question, I was looking for the answer 5.1 x E-14 F.

Here's why I think so: 


2. Correct

3. Using Fleming's right hand rule (since this is a proton), we can see that the force exerted on the proton is into the page, also represented by the following symbol:


Please feel free to PM me if you see any mistake (s) in my explanation and/or work shown.

Your turn!

[Krish2007]

You're right, I messed up my unit conversions on the first one.
Anyways,
1) Name a universal logic gate and explain what a universal logic gate is.
2) Briefly explain Kirchhoff's current law (the junction rule)
3) Determine the resistance between 2 points (a and b) if they are adjacent vertices of a regular tetrahedron. Assume that each edge of the tetrahedron has a resistance of one ohm.

[Creationist127]

You're right, I messed up my unit conversions on the first one.
Anyways,
1) Name a universal logic gate and explain what a universal logic gate is.
2) Briefly explain Kirchhoff's current law (the junction rule)
3) Determine the resistance between 2 points (a and b) if they are adjacent vertices of a regular tetrahedron. Assume that each edge of the tetrahedron has a resistance of one ohm.

Click to Show Answer

1. A gate that can implement a boolean operation without using any other gates, such as a NAND gate.
2. All the current going into a junction equals all the current leaving the junction; or, all the currents (with direction taken into consideration) add up to 0.
3. 0.5 Ω

[Krish2007]

You're right, I messed up my unit conversions on the first one.
Anyways,
1) Name a universal logic gate and explain what a universal logic gate is.
2) Briefly explain Kirchhoff's current law (the junction rule)
3) Determine the resistance between 2 points (a and b) if they are adjacent vertices of a regular tetrahedron. Assume that each edge of the tetrahedron has a resistance of one ohm.

Click to Show Answer

1. A gate that can implement a boolean operation without using any other gates, such as a NAND gate.
2. All the current going into a junction equals all the current leaving the junction; or, all the currents (with direction taken into consideration) add up to 0.
3. 0.5 Ω

All 3 are correct, your explanations for Kirchhoff's current law and universal gates were better than I could have put it myself.

Your turn!

[Creationist127]

1. Suppose you have an RC circuit consisting of a 9 volt battery, a 5 microfarad capacitor, and a 5 kiloohm resistor.
a. Give the time constant for the circuit.
b. Assuming the capacitor starts completely discharged, how long would it take to have 1 volt across the capacitor? 4.5 volts?
c. How long would it take for the capacitor to completely charge?

2. Using the laws of Boolean algebra, simplify this expression as much as possible:
(A*B*C) + A*(!B+!C)

3. Give the resistance (including tolerance) of a resistor with the following bands:
a. Red, green, blue, gold
b. Brown, white, orange, silver
c. Yellow, black, red

[azboy1910]

1. Suppose you have an RC circuit consisting of a 9 volt battery, a 5 microfarad capacitor, and a 5 kiloohm resistor.
a. Give the time constant for the circuit.
b. Assuming the capacitor starts completely discharged, how long would it take to have 1 volt across the capacitor? 4.5 volts?
c. How long would it take for the capacitor to completely charge?

2. Using the laws of Boolean algebra, simplify this expression as much as possible:
(A*B*C) + A*(!B+!C)

3. Give the resistance (including tolerance) of a resistor with the following bands:
a. Red, green, blue, gold
b. Brown, white, orange, silver
c. Yellow, black, red

Not sure, but.... (Click to Show Hidden Text)

1a. 0.025 s
1b. 0.0044 s for 1 volt across the capacitor. 0.0198 s for 4.5 volts across the capacitor.
1c. 0.0395 s

2. A?

3a. 25 megaohms, tolerance of 5%
3b. 19 kilohms, tolerance of 10%
3c. 4 kilohms 

[Creationist127]

1. Suppose you have an RC circuit consisting of a 9 volt battery, a 5 microfarad capacitor, and a 5 kiloohm resistor.
a. Give the time constant for the circuit.
b. Assuming the capacitor starts completely discharged, how long would it take to have 1 volt across the capacitor? 4.5 volts?
c. How long would it take for the capacitor to completely charge?

2. Using the laws of Boolean algebra, simplify this expression as much as possible:
(A*B*C) + A*(!B+!C)

3. Give the resistance (including tolerance) of a resistor with the following bands:
a. Red, green, blue, gold
b. Brown, white, orange, silver
c. Yellow, black, red

Not sure, but.... (Click to Show Hidden Text)

1a. 0.025 s
1b. 0.0044 s for 1 volt across the capacitor. 0.0198 s for 4.5 volts across the capacitor.
1c. 0.0395 s

2. A?

3a. 25 megaohms, tolerance of 5%
3b. 19 kilohms, tolerance of 10%
3c. 4 kilohms 

1. a. is right, but I got .0029 s and .017s for b., and I was looking for infinite time or something similar for c., as in an ideal system the capacitor will only approach, and never reach, fully charged.
2 is right, 3. a. and b. are right. 3. c. the numbers are right, but I've always seen that no fourth band means a tolerance of 20%.

Which one of us did 1. b. and c. wrong?

[azboy1910]

1. Suppose you have an RC circuit consisting of a 9 volt battery, a 5 microfarad capacitor, and a 5 kiloohm resistor.
a. Give the time constant for the circuit.
b. Assuming the capacitor starts completely discharged, how long would it take to have 1 volt across the capacitor? 4.5 volts?
c. How long would it take for the capacitor to completely charge?

2. Using the laws of Boolean algebra, simplify this expression as much as possible:
(A*B*C) + A*(!B+!C)

3. Give the resistance (including tolerance) of a resistor with the following bands:
a. Red, green, blue, gold
b. Brown, white, orange, silver
c. Yellow, black, red

Not sure, but.... (Click to Show Hidden Text)

1a. 0.025 s
1b. 0.0044 s for 1 volt across the capacitor. 0.0198 s for 4.5 volts across the capacitor.
1c. 0.0395 s

2. A?

3a. 25 megaohms, tolerance of 5%
3b. 19 kilohms, tolerance of 10%
3c. 4 kilohms 

1. a. is right, but I got .0029 s and .017s for b., and I was looking for infinite time or something similar for c., as in an ideal system the capacitor will only approach, and never reach, fully charged.
2 is right, 3. a. and b. are right. 3. c. the numbers are right, but I've always seen that no fourth band means a tolerance of 20%.

Which one of us did 1. b. and c. wrong?

(Click to Show Hidden Text)

 
Ok, so this is how I came up with my answers for 1b.

1b. 1 V/(63.2% x 9 V) x 0.025 s = 0.0044 s, 4.5 V/(63.2% x 9 V) x 0.025 s = 0.0198 s

This is most likely wrong, but this is just how I got my answers.

1c. I think you are right for this one because capacitors never really accomplish being fully charged as you said, although very close.