Basic Units of Measurement

Assessment

P1 (a): In the assignment P1 (a), the first statement is A circuit has an overall resistance of 2700O) and the power voltage applied across the circuit is 230V. Calculate Power.

The formula of power is W = V2 / R

Where

W= Power

V= Voltage

R=Resistance

Resistance =2700, Voltage= 230

Power = (230)2 /2700

Power = 19.5925 Watts

Statement 2: A current of 5 amps flows for 1 hour. Calculate Charge

To solve this problem, we need to revise the definition of electric current which suggests the formula.

The formula is I=q/t

Where

I= Current

q= Charge

t= time

Current= 5 amps, Time in seconds =1 hour = 60?60 =3600

Modifying the formula as per requirement, we get,

The formula is q=I?t

q= 5 ? 3600

q= 18000 C

Statement 3: A charge of 500 coulombs is transferred in 150s. Calculate Current.

The formula is I=q/t

I= Current

q= Charge

t= time

C= ?

q= 500, t= 150s

I= 500/150

I= 3.333333333 Amps

Statement 4: A charge of 800 coulombs is transferred across a potential difference of 12 V. Calculate energy.

V = W ÷ Q

Where

V is the potential difference in volts, V

W is the work done (energy transferred) in joules, J

Q is the charge in coulombs, C

V=12 V

Q= 800 C

W=?

V=12 V

Q= 800 C

W=?

Modifying the formula, we get,

W=V ? Q

W= 9600 J

(b) Write a short report on how the basic units of measurement, particularly those relevant to electrical work, are used and recognised in the everyday world. Use the intemnet to find information.

Basic Units Of Measurement

Length Units

The meter (m) is the SI base unit of length. The use of special names for decimal submultiples of the meter should be avoided, and units formed by attaching appropriate SI prefixes to the meter should be used instead.

The angstrom (Å) is equal to 10-10 m. Although it has been accepted for temporary use with the SI, it is preferable to replace this unit with the nanometer, using the relation 1 Å = 0.1 nm.

The nautical mile (nmi), equal to 1852 m, has been accepted for temporary use with the SI in navigation (BIPM, 2004, pp.198-218).

The foot (ft) is, as discussed above, the unit of length in the British systems of units, and it is also in customary use in the United States. Since 1959 the foot has been defined as exactly 0.3048 m. The yard (yd) is defined as exactly 3 ft or 0.9144 m.

Relative measurements of x-ray wavelengths formerly could be made to a higher accuracy than absolute measurements. Before 1965, most x-ray wavelengths were expressed in terms of the X-unit, which is approximately 10-13 m. The X-unit was superseded by the A* unit, which is based on the tungsten Ka1 line as a standard. The peak of this line is defined as exactly 0.2090100 A*. X-ray wavelength tables have been published in terms of this unit. At the time the A* unit was defined, it was thought to equal 10-10 m (the angstrom unit, Å) to within 5 parts per million, but the A* unit has since been determined to be about 15 parts per million larger than 10-10 m (Riehle, 2004, ...