Explore BrainMass

# DC

Direct current is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries, solar cells, commutator-type electric machines of the dynamo type. It can also flow in a conductor such as a wire, but can also flow through semiconductors, insulators, or through a vacuum. The DC current flows in a constant direction appose to alternating current (AC). Historically, direction current was called galvanic current.

Direct current may be found from an alternating current supply by use of a current-switching arrangement. This arrangement is called a rectifier. A rectifier contains electronic elements or electromechanical elements that allows current to flow only in one direction. DC may also be obtained from AC with an inverter or a motor-generator set.

Direct current is used in nearly all electronic systems as the power supply. Very large quantities of direct current power are used in the production of aluminum and other electrochemical processes. DC is also used in some railway propulsion. High-voltage direct current is used to transmit large amounts of power from remote generation sites or to interconnect alternating current power grids.

Although DC stands for direction current, it also can refer to constant polarity. Under this definition, DC voltage can vary in time. This can be seen in the raw output of a rectifier or the fluctuating voice signal on a telephone line. Some forms of direct current have almost no variation in voltage, although, it may still have variations in output power and current.

## BrainMass Categories within DC

### Potential divider and its Thevenin's circuit.

(a) A potential divider is to supply a voltage of 10 V, constant to better than 10%, into a load which can draw current up to a maximum of 50 mA. Design a potential divider for a 40 V battery (internal resistance 1 ohm) that would guarantee these conditions. (b) Determine Thevenin's circuit for the circuit of (a)

### eat generation and maximum thermal resistance of class A and B

The DC input power, heat generation and maximum thermal resistance of class A and B amplifiers are calculated. We know that the AC output power is 200 Watts, and that the Class A and Class B amplifiers operate with the maximum theoretical efficiency. We also know that the BJT power transistor has a maximum junction temperature

### Capacitors: D. C. Circuits

See attached image. Assume that E1=30V, E2=50V, E3=90V, C1=25 nF, C2=45 nF, C3=80 nF. Compute the charges Q1, Q2, and Q3 that builds on each of the capacitors C1, C2, C3, and also compute the charges q1, q2, and q3 that pass through the batteries E1, E2, and E3.

### q6

pease help with attached questions to understand . A computer memory stick has a power rating of 2.3*10^4 W and is connected to a 1.5V DC power supply for 6.5 hours. Determine: 1) the total charge that flows through the memory stick during this time 2) the number of electrons that flow through the memory stick

### Determining the initial angular acceleration of a coil

A uniform rectangular coil of total mass 270 g and dimensions 0.5m x 1.0m is oriented perpendicular to a uniform 3.90-T magnetic field (the figure). A current of 2.30 A is suddenly started in the coil. Find the initial angular acceleration of the coil just after the current is started (rad/s^2). See document attached for

### Electromagnetic Induction Lab

See attached lab report file. Please complete the graph for Step 9 under procedures (a graph of Primary Current vs. Galvanometer Deflection using the data from Steps 6 and 7) and provide results and conclusions. Please answer the four questions, the optional question and exercise.

### Expression for the magnitude and direction of a magnetic field

Please show all the work. Problem #1: A closed section of a wire in the shape shown in bold in the figure (attached) carries a uniform current I counterclockwise. This section of wire lies completely in the plane of the paper. The figure consists of three-quarters of a circle of radius R and two straight lines, both of len

### The Integral Form of Ampere's Law

Consider the induction B produced by an infinitely long straight current I. Choose a convenient closed path C in the plane perpendicular to the current and which does not enclose the current. Show by direct integration that given equality is correct in this case. CLOSED_INTEGRAL[B ? ds] = 0 See attachment for proper format

### A Series RC circuit is analysed and questions answered

A circuit (SEE ATTACHMENT) consists of a switch, a series resistance of R = 50 Ohms, connected to a parallel arrangement of two capacitors of 6 uF and 3 uF. The supply voltage source is 10V DC PART A: Calculate the time constant of the circuit PART B: What is the current flowing through the resistor straight after the swit

### Calculating the magnetic field and amount of current

Part 1: Solenoids produce magnetic fields that are relatively intense for the amount of current they carry. To make a direct comparison, consider a solenoid with 56 turns per centimeter, a radius of 1.15 cm, and a current of 0.110 A. Calculate the magnetic field at the center of the solenoid. Part 2: What current mus

### Inductance of Solenoid

A solenoid of inductance L is connected, via a resistance R, to a battery of fixed voltage V0. If the current is denoted by I(t), the voltage across the solenoid will be VL(t) = LdI/dt . The switch is closed at t = 0. (a) Determine I(t) and VL(t). (b) What is the total energy delivered to the solenoid between t = 0 and t = 1

### current and voltage drop

Please view the attached file to see the problem. 1a. For the circuit shown below, what is the value of the R4 resistor if the current at point a is 5 amps? 1b. What is the current at points b, c, and e? 1c. For the same circuit, what are the voltage drops across R1, R2, and R3?

### Bode Plot for a Transfer Function

Q9A 4: 1 step down transformer uses a 60 Vac source on the primary windings. There is 120 mA flowing through the load resistance on the secondary windings. That is the resistive load? a. 500 Ohms b. 2 K-Ohms c. 125 Ohms Q10: Sketch a Bode plot for the following transfer function (see attached). Q11: The outputs of tw

### Physics - Resistance Problem

1. This pre-lab explores the characteristics of wires in DC circuits. Keep in mind that an ordinary wire has low but finite resistance. For these questions assume the wire resistance is 0.1 Ohms, the power supply is an ideal 6V voltage source, and the light bulb resistance is 30 Ohms. A. For the circuit below, one such wi

### Op Amp Applications Derivations

Please see attached scan; this is a review from my electronics course; q1. Derivation and circuit for a non-inverted output. q2. Derivation of equation q3. derivation for gain showing high pass filter and breakpoint frequency q4. Derivation for gain showing high pass filter and the difference between an active filter and a f

### Comparing current from the battery

Please include all steps/reasoning. How does the current from the battery compare when the switch is open (and has been open for at least five minutes) and when the switch is closed (and has been closed for five minutes) in each of the circuits below? Explain. Please see attached file for full problem description.

### Axons and Action Potentials

Using the attached figure and the fact that it takes 8.0 x 10-12 J to raise the potential of the inner axon wall to +30 mV from -70 mV and another 4.3 x 10-11 J to restore the inner wall of the axon to -70 mV from +30 mV, find the power supplied to the axon per action potential.

### Basic Physics Problems (Force; Acceleration; Friction; Energy: Kinetic, Mechanical, Potential)

Question 1: A 1.5-kg object moves up the y-axis at a constant speed. When it reaches the origin, the forces F1 = 5.0 N at 37o above the +x-axis, F2 = 2.5 N in the +x-direction, F3 = 3.5 N at 45o below the -x-axis, and F4 = 1.5 N in the -y-direction are applied to it. (a) Will the object continue to move along the y-axis? (b) If

### D.C. Circuits: Resistances in Series, Parallel and Current

I need some help with these two problems: 9. Consider the shown below. If we make the nichronic wire longer, what happens to the: - (A) Equivalent resistance of the bulb (bulb B + wire) combination? - (B) Current through Bulb A? - (C) Voltage across Bulb B? - (D) Voltage across Bulb A? - (E) Current through Bulb B? In eac

### Capacitor with Variable Capacity: Gang Capacitor

Five 1-in^2 plates are arranged in attached file (Plates.jpg). The plate spacings are 0.01 in. The arrangement is to be used for a displacement transducer by observing the change in capacitance with the distance x. Calculate the sensitivity of the device in pico-farads per inch. Assume that the plates are separated by air.

### Magnitude and Direction of Net Force on Loop

A long straight wire carries a current of 31 A to the right. Next to the wire is a square loop with sides 1.0 m in length, as shown in the figure below. The loop carries a current of 2.7 A in the direction indicated. Calculate the magnitude and direction of the net force acting on the loop.

Question: Prove that the R-2R ladder network shown in the diagram (view attachment) has an output Vo of 2.5V.

### Analyzing the Circuit

Demonstrate by analysing the circuit that the inverse of a function can be generated by placing the function in the feedback loop of the op-amp. In the diagram, a logarithmic amplifier has been placed in the feedback loop. The output of the log amplifier is Vb=log(Va).

### Torque on a Current Loop

An 8 turn coil encloses an elliptical area having a major axis of 40.0 cm and a minor axis of 30.0 cm. The coil lies in the plane of the page and has a 5.75 A current flowing clockwise around it. If the coil is in a uniform magnetic field of 1.91 x 10^-4 T, directed toward the left of the page, what is the magnitude of the torqu

### Calculating Inductance and Maximum Current

Consider an RL circuit in which there's a 9.0 V battery, R = 5.5 ohms, L is unknown, and there's a switch that can be open or closed. When the switch is closed, the current in the circuit is observed to increase from 0 to 0.22 A in 0.15 seconds. (a) What is the inductance L? (b) How long after the switch is closed does the

### DC Circuits: Lightbulbs are Connected in Series

Three 25 ohms lightbulbs and three 100.0 ohms lightbulbs are connected in series. What is the total resistance of the circuit? What is their resistance if all six are wired in parallel?

### Transient Current

Suppose a 6 volt battery, a 10 ohm resistor, a 15 uf capacitor, and a switch are hooked up in series while the switch is open. The switch is closed at the same instant that a stopwatch is started. Describe what happens both qualitatively and as quantitatively as you can.

### Capacitors in Series Information

I have a question that I need a little help with. A 5.0 uf capacitor is connected to a 3.5 uf capacitor, and both of them are connected to a 6 volt battery. 1) what is the charge on each capacitor? What is the voltage on each capacitor? 2) With the battery still connected, the 3.5 uf cap is accidentally shorted out. As

### Capacitance: Capacitor circuit, charge distribution, brightness of the bulb

See attached file. What will happen in the capacitor circuit in the diagram? Include in your explanation what happens to the charge distribution on the capacitors as well as what happens to the brightness of the bulb. Remember that the capacitors are filled with insulator so charge cannot cross them.

### Resistance problems measuring current in a circuit

See attached files. 1. Find the current in each resistor in attachment #1 which is #27 on the page and it is circled. 2. Find a). the equivalent resistance of the circuit in the second Attachment or #47 on page and it is circle as well, b). each current in the circuit, c). the potential difference across each resisto