Answer:
Power, P = 30 W
Explanation:
We have,
Voltage drop of a circuit is 60 V
Resistance of the resistor is 120 ohms
Current across the circuit is 0.5 A
It is required to find the power conducted by the resistor. Power conducted by a resistor is given by :
V and I are voltage and current
So, the power conducted by the resistor is 30 watts.
Mercury looks pretty, in its shiny, fast-moving liquid form, but don't touch! It can be extremely poisonous to humans.
The symbol Hg that mercury is known by comes from its Greek name, hydrargyrum, which means "liquid silver" — to reflect its shiny surface. The element is also known as quicksilver for its mobility. Named after the fastest-moving planet in the solar system, mercury has been known to humanity for ages. In fact, evidence of its use has been found in China, India and Egypt, and traces of mercury were found in 3,500-year-old Egyptian tombs.
Mercury is a very toxic element. It can enter the body through an open wound or by inhaling or ingesting it. It can then cause damage to nerves, the liver and the kidney, as well as a number of other symptoms.
Despite its toxic qualities, mercury can still be useful to us. The element conducts electricity and is used in electrical switches of thermostats and certain types of doze alarm-type alarm clocks, according to the College of Natural Resources at the University of California, Berkeley (CNR) "The place where people probably see it most commonly is in the new light bulbs — the compact fluorescent light bulbs," where mercury vapor is one of the chemicals used, said Daniel King, an associate professor of chemistry at Drexel University.
Due to its high density and compactness, mercury is also used to make thermometers, barometers and other scientific instruments, according to the Jefferson Lab. However, for safety reasons, consumer use of mercury in thermometers has become less common over the years, as digital thermometers have been introduced. In 2008, 13 states introduced laws that limit the manufacture, sale and/or distribution of mercury fever thermometers: California, Connecticut, Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Hampshire, Rhode Island, Oregon, Washington, the Environmental Protection Agency reports.
Just the facts
Atomic number (number of protons in the nucleus): 80
Atomic symbol (on the Periodic Table of Elements): Hg
Atomic weight (average mass of the atom): 200.59
Density: 13.5336 grams per cubic centimeter
Phase at room temperature: Liquid
Melting point: minus 37.8 degrees Fahrenheit (minus 38.83 degrees Celsius)
Boiling point: 674.11 F (356.73 C)
Number of isotopes (atoms of the same element with a different number of neutrons): 34. Number of stable isotopes: 7
Most common isotope: 202Hg (29.9 percent natural abundance)
Mercury is typically found in the form of its common ore cinnabar — mercury sulfite — and can rarely be found on its own. To extract pure mercury, the ore is ground up and heated to the temperature of about 1,076 degrees F (580 degrees Celsius) with oxygen present in the process. Mercury vapor escapes from the ores and sulfur dioxide is removed, according to CNR. The metal is condensed and washed with nitric acid to purify it, and then distilled.
Mercury can form alloys with gold, silver, zinc and cadmium, which are called amalgams. Through those amalgams, mercury can be used to extract gold from rocks. When mercury comes into contact with gold, the gold dissolves into the mercury and then the two are separated, with the mercury being distilled off.
Mercury also forms compounds with other elements. Interestingly, one of such compounds — mercury nitrate — played a role in the coining of the term "mad as a hatter."
"Mercury was actually used in the making of hats from animal pelts," King said. In the 18th century people used the mercury nitrate compound to clean the pelts before they turned them into hats.
"And they discovered that a large percentage of the people who were working with those chemicals ended up suffering from brain damage," he said. "So the term 'mad as a hatter' actually comes from exposure to mercury."
Answer:
A)828.8Hz
B)869.2Hz
Explanation:
Here is a complete question;
What frequency is received by a person watching an oncoming ambulance moving at 115 km/h and emitting a steady 753 Hz sound from its siren? Speed of sound is 345m/s
b. What frequency does she receive after the ambulance has passed?
Vs= speed of the ambulance
, We convert to m/s for unit consistency
= 115 km/h= 115km× 1000m/1m × 1hr/3600s= 31.94m/s
Dopler effect is when observed frequency of wave changes with respect to the source or when observed moves relative to transmitting medium can be expressed as
f'=[ (v + vo)/(v- vs)]*f
=[ (v )/(v- vs)]*f
The sign vo and vs depends on vthe direction of the velocity
f= frequency of ambulance siren= 753Hz
v= speed of sound in air= 345m/s
Vo= speed of observer= 0
A) we are to determine the f' of ambulance as heard by person as ambulance approaching.
To find the frequency f' observed by the person we use the expresion below
Then substitute the values
f'=[ (v )/(v- vs)]*f
=[ (345)/(345-31.94)]×753
= 828.8Hz
B)What frequency does she receive after the ambulance has passed?
To find the frequency f' observed by the person we use the expresion below
Then substitute the values
f'=[ (v )/(v + vs)]*f
=[ (345)/(345 + 31.94)]×753
= 869.2Hz
=
