Electronics 1.0 (Introduction to Voltage, Current, and Power)

The energy between two points is the cost in energy (work done) required to move a unit of positive charge from the more negative point (lower potential) to the more positive point (higher potential).

Voltage

The energy released when a unit charge moves “downhill” from the higher potential to the lower.

Voltage

Voltage is also referred to as:

potential difference or electromotive force (EMF)

Unit of measure for voltage is:

Volt

This is done in moving a coulomb (C) of charge through a potential difference of 1 V.

A joule (J) of work

It is the unit of electric charge, and it equals the charge of approximately 6×10¹⁸ electrons.

Coulomb

It is the rate of flow of electric charge past a point

Current (I)

Unit of measure of current:

Ampere or amp (A)

By convention, current in a circuit is considered to flow from a more _______ point to a more _______ point,

even though the actual electron flow is in the opposite direction.

1. positive

2. negative

The electronic instrument which allows you to look at voltages (or occasionally currents) in a circuit as a function of time

Oscilloscope

Which law states that the sum of the currents into a point (node) in a circuit equals the sum of the currents out (conservation of charge).

Kirchhoff’s current law

It follows that, for a series circuit (a bunch of two-terminal things all connected end-to-end), the current is?

The current is the same everywhere

Things hooked in parallel (Figure 1.1) have the same ____ across them.

Voltage

Which law states that things hooked in parallel (Figure 1.1) have the same voltage across them. Restated, the sum of the “voltage drops” from A to B via one path through a circuit equals the sum by any other route, and is simply the voltage between A and B. Another way to say it is that the sum of the voltage drops around any closed circuit is zero.

Kirchhoff’s voltage law (KVL)

The power (energy per unit time) consumed by a circuit device is:

P = VI

This is simply (energy/charge) × (charge/time)

For V in volts and I in amps, P comes out in?

watts

A watt is a?

1 joule per second or J/s

Power goes into:

1. Heat (usually)

2. Mechanical work (motors)

3. Radiated energy (lamps, transmitters)

4. Stored energy (batteries, capacitors, inductors)

Managing the heat load in a complicated system (e.g., a large computer, in which many kilowatts of electrical energy are converted to heat, with the energetically insignificant byproduct of a few pages of computational results) can be a _____ part of the system design.

Crucial