Need Help About Dc Motor Circuit

Need help with DC circuit physics problem !!!?

Sum of the voltage drops around each loop = 0
Sum of the curents at each node = 0

1) You have (2) loops and (3) currents.
I1 = current going through V and R1
I3 = current going through R3
I4 = current going through R4

Going around the V, R1, R3 loop:..... Note: All loops are clockwise. Current going in the opposite direction is negative.
V - R1*I1 - R3*I4 = 0
Around the R3, R4 loop:
R3*I3 - R4*I4 = 0.... +R3*I3 because in this clockwise loop, the current is going in the opposite direction. The voltage drop is alread a negative, so the negative current makes it a positive.
At the node where I1, I3, and I4 split:
I1 (going in) - I3 (going out) - I4 (going out) = 0

So we have (3) equations with (3) unkowns, I1, I3, I4
V - R1*I1 - R3*I4 = 0
R3*I3 - R4*I4 = 0
I1 - I3 - I4 = 0

Solve by susbstitution... I'm going to cheat and use a calculator...
http://www.solvemymath.com/online_math_c...

I1 = 0.10 A
I2 = 0.05 A
I3 = 0.05 A

2) Now you have (3) loops... Again, all loops are done in the clockwise direction.
The V, R1, R2 loop
V - R1*I1 - R2*I2 = 0 <--- 1

The R2, R3 loop
R2*I2 - R3*I3 = 0 <---- 2

The R3, R4 loop
R3*I3 - R4*I4 = 0 <---- 3

The node above the switch
I1 - I2 - I3 - I4 = 0 <--- 4

With the calculator again
I1 = 9/80 A = 0.1125 A
I2 = I3 = I4 = 3/80 A = 0.0375 A

That's what I got... It's been awhile since I've done a DC circuit, but I should be correct.
Hope my explanation helped you understand the problem.

Physics Help! DC circuits!?

(a) For the initial current, you don't have to consider the capacitor. Just use Ohm's law: I = U/R = 0.2A.

(b) When the maximum charge is reached, there is no current, so you don't need to care about the resistor. Q = U*C = 4mAs.

(c) Here we have to solve a differential equation ;-)

dQ/dt = I = (U - Q/C)/R, thus

Q(t) = UC × (1 - exp ( -t / (RC)))

0.85 secons after the power on the charge is very close to the final charge, you will not be able to get a useful result with a simple calculator.

Q(0.85s) = 0.0039999999999999999986050953872022213.... As

This is 3×10^-17% less than the final charge after infinite time.

Can anyone help me on this dc circuits, again?

In Figures 1 and 2, all the resistor are connected in parallel.

The point is, it doesn't matter what shape or how long the connecting liens are -- they are considered to have Zero 0hms. [The only time this has any real effect is in highspeed switching circuits, like computers]

In Figure 3, the points D and E could be considered the "common" (sometimes called "ground" but "common" is more correct) point of the circuit. Again, in this case it doesn't matter what shape or how long the connecting lines are -- the 3-ohm and 4-ohm resistors are in parallel with each other.

Without my calculator, my best guess is that the voltage appearing at Point B (with D or E as common) is between 15 and 17 volts.

I need H-BRIDGE circuit to drive DC motor which type of H-BRIDGE nice ? can u please provide for me?

If you do not want to vary the speed then a chngeover switch will do the job. If you need to vary the speed then you need a variable DC source which has a reversable output. Sound like you need a simple DC drive, low power from Rapid Electronics at Colchester, for larger power give Control Techniques at Telford a call

I need help with a physics problem about AC/DC motors in VCRs?

Here is the question: Some motors must be able to switch directions, sometimes spinning clockwise and other times counter-clockwise. For example, the motor in a VCR must fast forward and rewind videotape. In these situations, explain which type of motor is the best choice.

Could someone please help me understand? Everyone is saying it's DC, but I don't understand why.

Electric Circuit question please need help asap?

When you say that with no resistance, the current = voltage, you are incorrect. The voltage will be at 3 volts while the current increases rapidly until something fails.
However, the "value" of current can equal the "value" of voltage only when the resistance = 1 ohm.

With no external resistance, Kirchoff's voltage rule states that the power source voltage (Vsource) must equal the sum of the voltage drop across any resistance of the motor's armature windings (Varmature) plus the back electro motive force voltage generated by the motor (Vemf). And the back emf voltage created by the motor is proportional to it's angular velocity.

Vemf = motor angular velocity * motor emf constant

Varmature = current * armature winding resistance

Vsource = Varmature + Vemf

The armature winding resistance of a dc motor is probably too low to measure with an ohmmeter. A technique known as the Kelvin Resistance Measurment would have to be used to calculate this value.

DC motor help! For electric vehicle!?

A Citroen 2CV or "deux cheveaux" (two horses) is so named because it has a 2 hp (1500W) motor. It may not accelerate like a Beetle 2.0 but it's great on l'essence (gas).

There are tons of off the shelf "electrical conversion kits" for motorcycles and cars. Just search for that term. As to where you'll get the power, well; batteries, and lots of 'em. The more you have the farther you can go. Sticking a small DC generator in there too might keep you from getting stranded.