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Electronics Information

A transistor works by allowing a small amount of current to control general current flow. Where is the small amount of current applied?

base

The transistor is the foundation of modern electronic devices. It is made entirely from semiconductor material (making it a solid state device) and can serve many different functions in a circuit including acting as a switch, amplifier, or current regulator. A transistor works by allowing a small amount of current applied at the base to control general current flow from collector to emitter through the transistor.

General Science

The fossil record is a product of which period of Earth's history?

Cambrian

The Cambrian period is one of the most significant geological time periods. Lasting about 53 million years, it marked a dramatic burst of changes in life on Earth known as the Cambrian Explosion. It is from this period that the majority of the history of life on Earth, as documented by fossils, is found. Called the fossil record, the layering of these mineralized imprints of organisms preserved in sedementary rock have allowed geologists to build a historical record of plant and animal life on Earth.

Mechanical Comprehension

If the force applied at the blue arrow over 5 ft. moves the green box 2.5 ft., what is the mechanical advantage of this lever?

Mechanical advantage (MA) can be calculated knowing only the distance the effort (blue arrow) moves and the distance the resistance (green box) moves. The equation is:

MA = \( \frac{E_d}{R_d} \)

where E_d is the effort distance and R_d is the resistance distance. For this problem, the equation becomes:

MA = \( \frac{5 ft.}{2.5 ft.} \) = 2

You might be wondering how having an effort distance of 2 times the resistance distance is an advantage. Remember the principle of moments. For a lever in equilibrium the effort torque equals the resistance torque. Because torque is force x distance, if the effort distance is 2 times the resistance distance, the effort force must be \( \frac{1}{2} \) the resistance force. You're trading moving 2 times the distance for only having to use \( \frac{1}{2} \) the force.

Math Knowledge

If side x = 12cm, side y = 9cm, and side z = 9cm what is the perimeter of this triangle?

30cm

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 12cm + 9cm + 9cm = 30cm

Word Knowledge

Jennifer's outspoken criticism of the meal disoncerted the waiter.

unnerve

To throw into confusion.

Word Knowledge

Anthology most nearly means:

collection

A collection of selected literary pieces.

Shop Information

Which of the following is not an advantage of using a tape measure over using a ruler?

measure with more accuracy

Rulers are used to both measure distance and to draw straight lines. Tape measures are flexible rulers useful for measuring longer distances and in tighter spaces. Rulers and tape measures provide similarly accurate measurements.

Word Knowledge

Derelict most nearly means:

destitute

Abandoned.

General Science

Leafy vegetables, beans, potatoes, fruits, and whole grains are good sources of:

fiber

Fiber provides bulk to help the large intestine carry away waste. Good sources of fiber are leafy vegetables, beans, potatoes, fruits, and whole grains.

Mechanical Comprehension

Coplanar forces:

act in a common plane

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.