Loads convert electrical energy into some other form of energy. Examples of loads include heating elements (heat), light bulbs (light), and solenoids (motion).
The choices represent four different diode symbols: (A) a zener diode, (B) a tunnel diode, (C) a photosensitive diode, and (D) a light-emitting diode (LED).
A hertz is a unit of measurement used to express the frequency (cycles per second) of alternating current. One hertz (Hz) is the same as one cycle per second. Choice (C) is incorrect because it indicates the rate of change in frequency rather than the frequency itself.
A conductor is an element that freely conducts electricity, whereas an insulator does not conduct electricity at all. A semiconductor is neither a good conductor nor insulator, but has some remarkable properties that make it very useful for making electronic components.
An earth ground is found outside a building, and normally utilizes conductors such as conduit or pipe that is already in the ground. All of the ground connectors in a residential wiring system will be attached to an earth ground, which is used to “funnel” away stray electricity in appliances and prevent it from causing electrical shock. A ground does not measure resistance.
In electron flow theory, electrons flow away from areas of excess negative charge to those with a deficiency of negative charge. When a conductor is connected across the terminals of a battery, the electrons in the conductor will be forced away from the negative terminal of the battery and toward the positive terminal. Therefore (C) is clearly wrong. Electrons can flow through solids and gases as well as liquids, so (A) is incorrect. While resistance can reduce the flow of electrons, it does not necessarily stop the flow completely, so (D) is incorrect.
Electrical pressure is known as voltage, and it is measured in volts (symbolized by the letter V).
This is the circuit symbol for an ohmmeter, (C), which is used to measure resistance.
This symbol represents a series-parallel circuit, which would have some components, such as an on/off switch, wired in series with a number of loads that are connected in parallel.
Ohm’s law tells us that V = I × R. If voltage stays constant, and resistance R rises, current I would have to drop.
Ohm’s law tells us that R = V ÷ I. If resistance R stays constant, and voltage V rises, current I will also have to increase.
Since V = I × R, and the current is the same across all the resistors, an increase in resistance must result in an increase in the voltage drop.
A capacitor is made to block DC (direct current), but allow AC (alternating current) to flow. Capacitive reactance is a capacitor’s “opposition” to the flow of current, and this tends to diminish as the frequency of alternating current increases.
The symbol for the transistor has an arrow that identifies the emitter. The direction of the arrow tells us what type of transistor it is; this is a PNP transistor.
An electromagnet’s magnetic field becomes stronger when more turns of wire are added to it, more current is passed through the coil, or an iron core is placed in the middle of the coil.
When current passes through a resistance, a voltage drop will take place. This represents an energy loss, and this energy is normally dissipated in the form of heat.
Ohm’s law states that voltage in volts is equal to the current in amperes multiplied by the resistance in ohms, or V = I × R. V represents voltage, and I represents current. Current is the rate of flow of electrons, or the intensity of the flow. (Specifically, I is the rate of charge flow.) Finally, R represents resistance.
When current flows freely through a diode, this is known as “forward bias.” If the orientation of the diode is such that it blocks current flow, that would be reverse bias. Open and grounded are irrelevant to the question that was asked.
A transistor has three connections: the base, the emitter, and the collector. The transistor is switched off and on by voltages applied to its base. When a voltage appears across the base-emitter junction, the transistor switches on and allows current to flow between the collector and emitter.
For a simple parallel circuit with four resistors of equal value, divide the resistance of a single component by the total number of components. For this parallel circuit, you have four 1,000 ohm resistors, so 1,000 ohms ÷ 4 = 250 ohms.