Basics Flashcards
What is the loose generalised distinction between the terms ‘electrical’ and ‘electronic’?
Loosely speaking, both terms relate to the use of electrical energy, but the two terms can be used slightly differently in different disciplines and in different countries.
Within reason, we can say:
Electrical - often used to refer to applications concerned with the generation, transmission or use of large amounts of electrical energy.
Electronic - used for applications involving smaller amounts of power. In many cases, the electrical energy is used to convey information rather than as a source of power.
What is the Systems Approach?
The Systems Approach combines the Systematic approach (breaking a complex problem into to smaller and smaller easily understood sub-systems) with an understanding of S**ystemic issues (chatacteristics that are features of the system as a whole).
A key feature being that it places as much importance on the relationships between components, as it does on the components themselves.
In electrical/electronics what is meant by the word system?
In an engineering context, a system can be defined as a closed volume for which the inputs and outputs are known. This concept is very flexible in its applications, but the term is notmally reserved for arrangments that perform some useful function.
What aspects of electrical and electronic systems fall within the realm of generation?
Electrical
(usually production of electricity for use as a power source)
- Electrical generators in power stations or hydroelectric dams etc.
- Smaller units such as altenators in cars etc.
Electronic
(usually production of electrical signals used to represent physical quantities, rather than as source of power)
- Sensors that produce electrical signals in response to changes in their environment. e.g. photodiode.
What aspects of electrical and electronic systems fall within the realm of Transmission?
Electrical
(often concerned with the distribution of electrical power)
- Overhead or underground cables.
- Thick copper wires in smaller applications.
Electronic
(more often concerned with the transmission of information)
- Electrical wires or optical cables.
- Alternatively, radiowaves or microwaves.
What aspects of electrical and electronic systems fall within the realm of control or processing?
Control is related to command and regulation functions. Varies from the simplest form of control, a switch, to far more complex forms of control.
Electrical
- regulation or variance of power supplied to certain apparatus.
Electronic
- performance of complex processing functions, perhaps using computer based techniques.
What aspects of electrical and electronic systems fall within the realm of utilisation?
Utilisation is concerned with the use of electrical energy to perfom some useful function. Widely varied set of elements that produce the required output of a system.
Electrical
- production of heat, light or motion.
Electronic
- production of sound or the display of visual information
What is the Quantity Symbol, the SI Unit and the Unit Symbol for Capacitance?
Pay attention to capitalisation and italicisation.
Quantity - Capacitance
Quantity Symbol - C
Unit - farad
Unit Symbol - F
What is the Quantity Symbol, the SI Unit and the Unit Symbol for Charge?
Pay attention to capitalisation and italicisation.
Quantity - Charge
Quantity Symbol - Q
Unit - coulomb
Unit Symbol - C
What is the Quantity Symbol, the SI Unit and the Unit Symbol for Current?
Pay attention to capitalisation and italicisation.
Quantity - Charge
Quantity Symbol - I
Unit - ampere
Unit Symbol - A
What is the Quantity Symbol, the SI Unit and the Unit Symbol for Electromotive Force?
Pay attention to capitalisation and italicisation.
Quantity - Electromotive Force
Quantity Symbol - E
Unit - volt
Unit Symbol - V
What is the Quantity Symbol, the SI Unit and the Unit Symbol for Frequency?
Pay attention to capitalisation and italicisation.
Quantity - Frequency
Quantity Symbol - f
Unit - hertz
Unit Symbol - Hz
What is the Quantity Symbol, the SI Unit and the Unit Symbol for Inductance (self)?
Pay attention to capitalisation and italicisation.
Quantity - Inductance (self)
Quantity Symbol - L
Unit - henry
Unit Symbol - H
What is the Quantity Symbol, the SI Unit and the Unit Symbol for Period?
Pay attention to capitalisation and italicisation.
Quantity - Period
Quantity Symbol - T
Unit - second
Unit Symbol - s
What is the Quantity Symbol, the SI Unit and the Unit Symbol for Potential Difference?
Pay attention to capitalisation and italicisation.
Quantity - Potential Difference
Quantity Symbol - V
Unit - volt
Unit Symbol - V
Discuss electromotive force (e.m.f.) and potential difference.
(sorry, not brief)
electromotive force (e.m.f.) is the stimulus that causes an electric current (electrons) to flow around a circuit. The e.m.f. represents the energy introduced to a circuit by a source (e.g. battery or generator).
The energy transferred from the source to the load results in a change in the electrical potential at each point in the load. Between any two points in the load there will exist a certain potential difference, which represents the energy associated with the passage of a unit of charge from one point to the other.
Both e.m.f. and potential difference are expressed in units of volts, which highlights that the two quantities are related. Figure below illustrates: e.m.f. is the quantity that produces an electric current, while potential difference is the effect on te circuit of this passage of energy.
Briefly discuss voltage reference points.
hint: it’s beneath you.
Electromotive forces and potential differences in circuits produce different potentials (voltages) at different points in the circuit. It is normal to describe the voltages throughout a circuit by giving the potential at a particular point with respect to a single reference point.
This reference point is often called the ground or earth of the circuit. The voltage on the ground itself is zero, therefore the ground is also called the zero volt line.
Define and explain Kirchhoff’s Current Law.
“At any instant, the algebraic sum of all the currents flowing into any junction in a circuit is zero.”
Σ I = 0
If we assume for example that current flowing into a junction is positive, then we can take from this that any current flowing out of a junction is negative. Furthermore, the sum of the current flowing into a junction is equal in magnitude to the sum of the current flowing out of a junction.
A junction is any point where electrical paths meet.
The law come about from consideration of conservation of charge (the charge flowing into a point must equal that flowing out).
Briefly discuss Kirchhoff’s Voltage Law.
“At any instant, the algebraic sum of all the voltages around any loop in a circuit is zero.”
Σ V = 0
The term loop refers to any continuous path around the circuit, and the law comes about from consideration of conservation of energy.
It is important that the various quantities are assigned the correct sign. Assuming for example that clockwise voltages are considered positive then *counterclockwise* voltages must benegative**.
Discuss the instantaneous power dissipation P of a resistor.
i.e. the relationship of P, V and I
The instantaneous power dissipation P of a resistor is given by the product of the voltage across the resistor and the current passing through it.
P = VI
Combining with Ohm’s Law gives a range of expressions:
P = I2R
P = V2/R
How do you calculate the resistance of a number of resistors in series?
The effective resistance of a number of resistors in series is equal to the sum of their individual resistances.
R = R1 + R2 + R3 + … + Rn
How do you calculate the resistance of a number of resistors in parallel?
The effective resistance of a number of resistors in parallel is given by the following expression:
1/R = 1/R1 + 1/R2 + 1/R3 + … + 1/Rn
Note: the effective resistance of a number of resistor in parallel will always be less than that of the lowest-value resistor.
