Circuit Lab B/C

[Creationist127]

1. A capacitor has 1 cm^2 plates, .5 mm apart from each other (with nothing in between). What is its capacitance?
2. A resistor is a cylinder with 5 mm diameter and is 1 cm long, and has resistivity 1 Ω*m. What is its resistance?
3. The resistor and capacitor are placed in series with each other and a 9-volt battery. How long will it take for the capacitor to charge to 8.5 volts?

Click to Show Answer

1. 1.77E(-10) F or 0.177 nF
2. 509.3 ohms
3. about 2.89 time constants

I worded q1 badly, I really meant "square, 1 cm to a side", but as "1 cm^2" your answer is right. 2 is right, and I was looking for an actual time (in seconds) for 3.

[azboy1910]

1. A capacitor has 1 cm^2 plates, .5 mm apart from each other (with nothing in between). What is its capacitance?
2. A resistor is a cylinder with 5 mm diameter and is 1 cm long, and has resistivity 1 Ω*m. What is its resistance?
3. The resistor and capacitor are placed in series with each other and a 9-volt battery. How long will it take for the capacitor to charge to 8.5 volts?

Click to Show Answer

1. 1.77E(-10) F or 0.177 nF
2. 509.3 ohms
3. about 2.89 time constants

I worded q1 badly, I really meant "square, 1 cm to a side", but as "1 cm^2" your answer is right. 2 is right, and I was looking for an actual time (in seconds) for 3.

My bad, I misread that the same resistor and capacitor from questions 1 and 2 were used for question 3, I thought that they were separate. Sorry about that!

Edit: Anyway I believe the answer then would be

Click to Show Answer

about 2.605E(-7) seconds

[Creationist127]

Click to Show Answer

1. 1.77E(-10) F or 0.177 nF
2. 509.3 ohms
3. about 2.89 time constants

I worded q1 badly, I really meant "square, 1 cm to a side", but as "1 cm^2" your answer is right. 2 is right, and I was looking for an actual time (in seconds) for 3.

My bad, I misread that the same resistor and capacitor from questions 1 and 2 were used for question 3, I thought that they were separate. Sorry about that!

Edit: Anyway I believe the answer then would be

Click to Show Answer

about 2.605E(-7) seconds

Looks good, your turn!

[azboy1910]

1. Draw a Thevenin equivalent circuit for the circuit below using R5 as the load resistor.

2. An electromagnet with a turn density of 1.5k turns/meter with a current of 50 mA passing through it has a nickel core (100 H/m). Calculate the magnetic field strength of the electromagnet.
3. Two wires are made of the same material and are of the same length. However, one of the wires (W1) has double the diameter than the other wire (W2). Assuming all other factors that would affect the resistance of these wires are the same for both wires, how many times greater is the resistance of W2 than W1?

[UTF-8 U+6211 U+662F]

1. Draw a Thevenin equivalent circuit for the circuit below using R5 as the load resistor.

2. An electromagnet with a turn density of 1.5k turns/meter with a current of 50 mA passing through it has a nickel core (100 H/m). Calculate the magnetic field strength of the electromagnet.
3. Two wires are made of the same material and are of the same length. However, one of the wires (W1) has double the diameter than the other wire (W2). Assuming all other factors that would affect the resistance of these wires are the same for both wires, how many times greater is the resistance of W2 than W1?

Click to Show Answer

1. 0.5 V battery in series with the load and a 3.38 ohm resistor?
2. 7500 T?
3. W2 is 4x the resistance of W1.

[azboy1910]

1. Draw a Thevenin equivalent circuit for the circuit below using R5 as the load resistor.

2. An electromagnet with a turn density of 1.5k turns/meter with a current of 50 mA passing through it has a nickel core (100 H/m). Calculate the magnetic field strength of the electromagnet.
3. Two wires are made of the same material and are of the same length. However, one of the wires (W1) has double the diameter than the other wire (W2). Assuming all other factors that would affect the resistance of these wires are the same for both wires, how many times greater is the resistance of W2 than W1?

Click to Show Answer

1. 0.5 V battery in series with the load and a 3.38 ohm resistor?
2. 7500 T?
3. W2 is 4x the resistance of W1.

Click to Show Answer

Ok, so here's what I got.

1. I got a 0.88 V battery in series with the load and a 3.06-ohm resistor.
2. I got 0.0094 T as an answer from the equation below:

(1500 turns/m)(50 mA/1000)(100 H/m)(4pi x 10^-7 H/m) = 0.0094 T 
3. Correct 

Let me know if you disagree. If not, your turn!

[UTF-8 U+6211 U+662F]

1. Draw a Thevenin equivalent circuit for the circuit below using R5 as the load resistor.

2. An electromagnet with a turn density of 1.5k turns/meter with a current of 50 mA passing through it has a nickel core (100 H/m). Calculate the magnetic field strength of the electromagnet.
3. Two wires are made of the same material and are of the same length. However, one of the wires (W1) has double the diameter than the other wire (W2). Assuming all other factors that would affect the resistance of these wires are the same for both wires, how many times greater is the resistance of W2 than W1?

Click to Show Answer

1. 0.5 V battery in series with the load and a 3.38 ohm resistor?
2. 7500 T?
3. W2 is 4x the resistance of W1.

Click to Show Answer

Ok, so here's what I got.

1. I got a 0.88 V battery in series with the load and a 3.06-ohm resistor.
2. I got 0.0094 T as an answer from the equation below:

(1500 turns/m)(50 mA/1000)(100 H/m)(4pi x 10^-7 H/m) = 0.0094 T 
3. Correct 

Let me know if you disagree. If not, your turn!

Oops (Click to Show Hidden Text)

1. I broke the circuit at the battery instead of shorting it out. I am now getting 3.06 ohms. Also for the voltage, I forgot to remove R5, I am now getting the same answer as you.
2. The magnetic field is permeability times turns per length times current, so I believe it would be (1500 turns/m)(0.05 A)(100 H/m) = 7500 T. I believe your equation doesn't work out dimensionally because you multiplied by an extra H/m instead of replacing the permeability of free space with the permeability of nickel.

Next question: What is a relay and how does it work?

[Krish2007]

Next question: What is a relay and how does it work?

Click to Show Answer

A relay is an electrically controlled switch, kind of like a transistor. It can work in multiple ways, but one way (the most common way?) is for it to use an electromagnet. The electromagnet controls the switch by moving a conductor into position to close the switch and allow current flow.  

[UTF-8 U+6211 U+662F]

Next question: What is a relay and how does it work?

Click to Show Answer

A relay is an electrically controlled switch, kind of like a transistor. It can work in multiple ways, but one way (the most common way?) is for it to use an electromagnet. The electromagnet controls the switch by moving a conductor into position to close the switch and allow current flow.  

Yep, your turn!

[Krish2007]

1) Which of the famous scientists in the rules found that electricity could be produced chemically?
2) List 4 properties of an ideal op-amp.
3)
Find V₁ and V₂.