MODULE 3: ELECTRIC CURRENT AND E;ECTRIC CIRCUIT

ELECTRICAL CIRCUIT

A complete path traversed by an electric current. It is a path in which electrons flow from a current source

circuit

It is an unbroken loop of conductive material that allows charge carriers to flow through continuously without beginning or end. It is a simple closed loop through which charges are allowed to move freely.

broken

If a circuit is "———," that means its conductive elements will no longer form at complete path, and continuous charge flow cannot occur in it. Its location in a circuit is irrelevant to its inability to sustain continuous charge flow.

Ohm's Law and Kirchhoff's Rules

Two of the basic laws that mathematically describe the performance of electric circuits?

Gustav Kirchhoff

a German Physicist who contributed to the fundamental understanding of electrical circuits, spectroscopy, and the emission of black-body radiation by heated objects.

Kirchhoff's rules

two statements about multi- loop electric circuits that embody the laws of conservation of electric charge and energy and that are used to determine the value of the electric current in each branch of the circuit

junction theorem

states that "total current entering a junction or node is exactly equal to the charge leaving the node, thus no charge is lost within the node". In this rule, the sum of the currents into a specific junction in the circuit equals the sum of the currents out of the same junction.

junction theorem

Electric charge is conserved: it does not suddenly appear or disappear; it does not pile up at one point and thin out at another.

loop equation

states that "in any closed loop network, the total voltage around the loop is equal to the sum of all voltage drops within the same loop" which is also equal to zero.

loop equation

states that around each loop in an electric circuit the sum of the emf's (electromotive forces, or voltages, of energy sources such as batteries and generators) is equal to the sum of the potential drops, or voltages across each of the resistances, in the same loop. All the energy imparted by the energy sources to the charged particles that carry the current is just equivalent to that lost by the charge carriers in useful work and heat dissipation around each loop of the circuit.

series and parallel

two basic electric circuit arrangements

conductive wire

used to establish relation among source of voltage and load.

ON / OFF switch and a fuse

used in between the source and load

Closed Circuit

This has a complete path for current to flow. When load works on its own in a circuit then it is called ———-. Under this situation, the value of current flow depends on load.

Open Circuit

This is a circuit having an incomplete path. These are not functional. When a circuit is open, the current cannot flow through.

Short Circuit

Is a circuit that allows the current to travel along an unintended path. In this way, it encounters little (or no) resistance. The piece of the circuit bypassed by this may cease to function and a large amount of current may begin flowing.

low-resistance path

usually made unintentionally, that bypasses part of a circuit.

Series Circuit

A circuit in which the same current flows through all components of the circuit. When 2 or more loads or resistors are connected to each other in a series.

series circuit

If the lights are constructed in a ———, when one bulb is missing or burnt out, the current cannot flow, and all lights will not turn on.

Resistor

In a series circuit, it is anything that uses some of the power from the cell.

series circuit

The main disadvantage of a ——— is that if there is a break in the circuit the entire circuit is open, and no current will flow.

voltage drop

the amount the voltage lowers when crossing a component from the negative side to the positive side in a series circuit.

Parallel Circuit

A circuit in which the components are arranged so that the current must break up before meeting and combining again.

charge

(Parallel Circuit)

Because the current divides, each component is assured a ——-. And if one path breaks, the other paths will still work because they aren't reliant on each other.

resistor

In a Parallel Circuit, there is more than one ——- (bulb) and they are arranged on many paths.

Parallel Circuit

electricity (electrons) can travel from one end of the cell through many branches to the other end of the cell.

input supply

In Parallel Circuit, the voltage capacity of all loads must be equal to ———.

Parallel Circuit

Power of "load" can be different. In a parallel circuit, if one load or bulb gets fuse, then rest of the bulbs will still get power supply and will glow.

resistance

Parallel Circuit has two or more paths for current to flow through. the flow of electricity is divided between each according to the —— along each route

Parallel Circuit

In this type of circuit, the voltage is the same across each component of the parallel circuit. The voltage will be the same anywhere in the circuit.

Parallel Circuit

In this type of circuit, the voltage across each element is the same, and equal to the source voltage, and the current though each element varies according to the impedance of each element

Kirchoff’s Current Law (KCL)

What rule is applied when the total current flowing from the source is equal to the sum of the individual currents flowing through each parallel element?

series circuit

In this type of circuit, the current through each series element is the same, and equal to the source current, while the voltage across each series element varies according to the impedance of each element.

Kirchoff's Voltage Law

What rule is applied when the voltage supplied by the source is equal to the sum of the individual voltage drops across each series element.

Branch Circuit

the circuit conductor between the final over current protection device and the outlets.

Branch Circuit

the wiring installed between the circuit over current protective device (fuse, or circuit breaker) and the outlets.

General purpose branch circuit

Supplies two or more outlets for lighting and appliances, including convenience receptacles.

Appliance branch circuit

Supplies outlets intended for feeding appliances. Fixed lighting however is not supplied.

Appliance branch circuit

Designed for powering electric appliances and devices through plug in receptacles, with its own circuit breaker.

Individual branch circuit

A branch circuit that supplies only one utilization equipment.

Individual branch circuit

Designed specifically for powering a single, higher power electric consuming device or equipment such as oven, dryer or HVAC system.

Flexibility of the circuit

Considerations of a Good Circuit Design

Installation can all probable pattern arrangements and location of the loads for expansion, or for future development.

Reliability and efficiency of service

Considerations of a Good Circuit Design

Must have a continuous service and supply of power that are all dependent on the wiring system.

utility service and building electric system

Reliability of electric power in a facility is determined by two factors

Safety of the circuitry

Considerations of a Good Circuit Design

independent service can be used in lieu of emergency equipment as backup for normal services.

Economy as to cost

Considerations of a Good Circuit Design

Refers to the initial cost as well as the operating cost. These are two cost-factors stand in inverse relationship to one another. Over design is as bad as under design.

Energy

Considerations of a Good Circuit Design

energy law and codes, budget, energy conservation technique and energy control.

Space

Considerations of a Good Circuit Design

must consider the following easy maintenance, ventilation, expandability, centrality, and limitation of access