Explore BrainMass

Ohm's Law

Ohm’s law states that the current through a conductor between two point is proportional to the potential difference across the points. This principle introduces the constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship.

I = V/R


I is the current

V is the potential different across the conductor

R is the resistance

Ohm’s law states that the R is this relation with constant independence of the current.

In physics, the term Ohm’s law is also used to refer to various generalizations of the law originally formulated by Ohm.

J = σE


J is the current density

E is the electric field

σ is the conductivity

Calculating the Resistance of the Resistor

The resistance of a resistor is to be determined by measuring the voltage drop across it when passing a given current, as shown in the figure in the attachment. The instrument indications are 2 mA and 12.0 V, the ammeter having a resistance of 10 Ω and the voltmeter a resistance of 10kΩ. Calculate: (a) the resistance of

Ammeter-Voltmeter Method

The resistance of a coil is measured by the ammeter-voltmeter method. With the voltmeter connected across the coil, the readings on the ammeter and voltmeter are 0.4A and 3.2 V respectively. The resistance of the voltmeter is 500 Ohm. Calculate (a) the true value of the resistance and (b) the percentage error in the value of the

Norton and Thevenin Equivalent

Please see attached. Given the one-port network. The output port of the one-port is defined by terminals A and B. a) Find the Thevenin and Norton Equivalent circuits. b) Plot the current voltage characteristic of the one-port.

Electric Circuits: Loop Analysis

Please see attached problem and solve all parts using Loop Analysis only. Find all the currents in the circuit. Indicate all the voltage polarities and current directions.

Electric Circuits Resistors

A circuit consists of two 100 ohm resistors in series. What is the voltage across each resistor when a. The current through the resistors is 10 mA? b. The current through the resistors is 50 mA?

resistance of telephone line

A circuit consists of a 48 volt battery at a telephone company central office which is connected to a twisted pair telephone line. At the other end of the line is a telephone handset with a resistance of 1000 ohms. The twisted pair has a loop resistance of 100 ohms per kilometer. (Loop resistance is the combined resistance

Physics: Electric Circuit Questions

See attached file. In the circuit shown in the attachment E=60V, R_1=40 Ohms, R_2=25 Ohms and L=0.3H. Switch S is closed at t=0 s. Just after the switch is closed a) What is the potential difference across the resistor R_1? b) Which point (a or b) is at higher potential? c) Find potential difference across the inductor (

Ohm's Law Problem

See attached file. I have conducted an experiment for Ohm's Law. Based on my data, please to answer the following three questions for series and parallel and a brief conclusion of results. No graphs are required. 1. From measured values of current and voltage compute the resistances R1, R2 and R3 for both series and p

Directly and Inversely Proportional

Hello, I cannot figure this out. Please help. Directly and Inversely Proportional A well known physical law describing the relationship between electrical current, voltage and resistance in a circuit is called Ohm's law, which can be paraphrased as follows: The current in a circuit is directly proportional to the vo

Trans-impedance Amplifier

(a) The circuit of FIGURE 2 (attached) is known as a trans-impedance circuit used for the measurement of very small currents. Derive the relationship between the output voltage V and the input current I; i.e. if V = kI find k in terms of R1, R2 and Rf. (b) Calculate the current I if Rf =10 mOhm (milli-Ohms), R1 = 90 kOhm, R2=

Analysis of Reflections on a Transmission Line

A transmission line of length l, characteristic impedance Z0 = 100 Ohm, and one-way time of flight T = l/c is connected at z=0 to a 100 volt DC battery through a series source resistance Rs = 100 Ohm and a switch. The z=l end is loaded by a 300 Ohm resistor. a) The switch at the z=0 end has been closed for a very long time so

Calculating Source Impedance for a Transformer for Max Power

A large power transformer has a turns ratio N1/N2 of 1:5. When the primary voltage is 400 V and it is connected to a resistive load, its secondary current is 100 A. Calculate the required value of source resistance of the supply to give maximum power transfer.

Electricity Topics: Fields, Resistance, Series and Parallel

Q1(a) Define Electric current and quote its units as defined by SI quantities Q1(b) In a device if N = 5.4 x 10^6 electrons pass in a time of t = 40 ms determine the current that this equates to Q2(a) A calculator uses 50 uA of current in 300 ms with an applied voltage from a battery of 3.5V Calculate the number of el

Current through resistors wired in parallel

A 20 volt battery is connected to two resistors that are wired in parallel. The resistor values are 120 Ohms and 60 Ohms. a. What is the current delivered by the battery? b. What is the current through the 120 Ohms resistor? c. What is the current through the 60 Ohms resistor?

Current in series circuit

A 12 volt battery and two resistors are wired in series. The resistor values are 80 Ohms and 40 Ohms. a. What is the current through the resistors? b. What is the voltage across the 80 ohm resistor? c. What is the voltage across the 40 ohm resistor?

Circuit Analysis: Electronically-Controlled Switch

See the attached file. In the circuit of attached figure, S1 is an electronically-controlled switch. It closes at time t = 0 seconds and opens again at time t = 50 milliseconds. (a) Determine the currents I1, I2 and I3: (i) under steady-state conditions, e.g. after about `5 time constants'. (ii) at the instant the switch i

Calculate Measured Resistance: Ohm's Law Example

Calculate the measured resistance of a resistor and verify the Ohm's law. Please see attached file. On a separate piece of graph paper, plot V against I and connect the points with a smooth curve. The V-I curve for two elements in series can also be calculated from the V-I curve of the individual elements. For a given value o

Resistors in Series

Part 1 Three resistors, 13.7 Ω, 44.1 Ω, and R, are connected in series with a 18.0 V battery. The total current flowing through the battery is 0.122 A. Calculate the value of resistance R. Part 2 Calculate the potential difference across R.

Ohm's Law: Shocking Voltage

Part 1 A person notices a mild shock if the current along a path through the thumb and index finger exceeds 87.6μA. Calculate the maximum allowable voltage without shock across the thumb and index finger with a dry-skin resistance of 3.25E+5Ω. Part 2 Calculate the maximum allowable voltage with a wet-skin resistance

Current Electricity: Ohm's law and resistance

Part 1 A typical cell membrane is 7.86 nm thick and has an electrical resistivity of 1.28E+7 Ω*m. If the potential difference between the inner and outer surfaces of a cell membrane is 71.7 mV, how much current flows through a square area of membrane 1.16 μm on a side? Part 2 Suppose the thickness of the memb

Ways to increase the current through a circuit

Ohm's Law describes the relationship between current, voltage and resistance. Using this relationship, explain how you would increase the current through a circuit. (a) lower the voltage or lower the resistance (b) raise the voltage, but only if you raised the resistance by the same factor (c) raise the voltage or lower

Physics Circuits: charging time, voltage, current flow, discharge

Please see the attached problem. Consider the following transient RC-circuit and answer these questions in the given order. 1) Find charging the constant. 2) Find full-charged time. 3) Find charging equations. 4) Find voltage across and current flow for capacitor at t = 4 second/charging. 5) Find discharging ti

Resistance of a Wire

What the starter motor on a car is engaged, there is a 300 A current in the wires between the battery and the motor. Suppose the wires are made of copper and have a total length of 1.0m. What minimum diameter can the wires have if the voltage drop along the wires is to be less than 0.50V?

DC Circuits - Networks

The power in a resistor RLOAD of 10Ω when connected to a 100 volt supply is measured using a voltmeter and ammeter. There are two possible ways of connecting the meters (see attachment). The resistances RA and RV represent the internal resistances of the ammeter and voltmeter respectively. When connected as in (a) (see

C++ program calculating current through a set of resistors

Writing a Program using Input and Output Arrays Procedure: 1. You will write one C program. Name it as YOUR LAST NAME_Lab07.cpp 2. Lab07 will be used to calculate the current that flow through five separate resistors based on a user's input of voltage (using Ohm's Law). It will use two "input arrays" and produce one "

Current Electricity: Ohm's Law and resistances in parallel.

Suppose that a person's body resistance is 780 . (a) What current passes through the body when the person accidentally is connected to 110 V? (b) If there is an alternative path to ground whose resistance is 50 , what current passes through the person? (c) If the voltage source produces 1.5 A, how much current p

Derivatives to Calculate the Rate of Change

The voltage, V, (in volts) across a circuit is given by Ohm's law: V = IR, where I is the current (in amps) flowing through the circuit and R is the resistance (in ohms). If we place two circuits, with resistance R1 and R2, in parallel, then their combined resistance, R, is given by 1/R = 1/R_1 + 1/R_2 Suppose the current is