100 points to right
a student is measuring the effects of an electric circuit on a compass, and he is testing to see if increasing the current will cause the compass needle to change its direction faster. he does one trial using a 9-volt battery and another trial using a 1.5-volt battery. he takes accurate data. based on good experimental design, which would improve his experiment?

a)he should use only one battery but do several trials, using different circuit designs to ensure he has appropriate test groups.

b)he should repeat the test with three additional batteries of varying voltages to demonstrate the reproducibility of results.

c)he should use batteries of the same voltage but from different manufacturers, to show he has used different variables.

d)he should add a nonworking compass to act as a control.

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.

the answer is 303.15 or 303