Waves
What is a wave?
A rhythmic disturbance that propagates through a medium or space
Give one example of an insulator
Examples plastic, rubber, wood
Which method of heat transfer occurs through direct contact of solids?
Conduction
List the two main types of energy.
Potential and Kinetic energy
Differentiate between mechanical and electromagnetic waves
Mechanical wave requires medium
Electromagnetic waves do not require medium
Differentiate between the direction of electron flow and the direction of conventional current
Electron flow negative to positive
Conventional current positive to negative
Convert 25° C to Kelvin
Temp in K = ° C + 273 = 25° C + 273 = 298 K
What is the SI BASE unit of work done?
W = Fd = kgms-2m = kgm2s-2
List parts of (i) longitudinal and (ii) transverse wave
Longitudinal: rarefraction and compression
Transverse: crest and trough
State Kirchoff's Law
Kirchoff's Law states that the total current entering a junction is equal to the total current leaving the junction
What is the range of the clinical thermometer?
35°C to 42°C (94°F to 108°F)
State law of conservation of energy
Energy can neither be created or destroyed only transferred from one form to another
Define:
- amplitude
- wavelength
- period
- frequency
Amplitude distance from midpoint to crest or trough
Wavelength distance of one complete wave
Period time taken for one complete wave oscillation
Frequency number of cycles per unit time
A charge of 50 mC flows past a point in a wire 5μs. Determine current in kA
I - Q/t = 50 x 10-3 C/5x10-6s = 10,000 A = 10kA
Determine the specific heat capacity of ethanol if 4kg of the liquid absorbs 384 kJ of energy changing the temperature from 30° C to 70° C.
c = EH/mΔ T = 384 x103J/(4kg)(40K) = 2400 J/kg K
A helicopter of mass 2000 kg is at a height of 350 m above the Earth what is the gravitational potential energy in MJ?
GPE = 2000 kg x 9.8 m/s2 x 350 m = 6,860,000 J = 6.86 MJ
Calculate the wavelength of an electromagnetic wave in a vacuum that emits a frequency of 316 MHz. (Give answer to 2 sf)
v = fλ
λ =v/f = 3x108 ms-1/316 x 106 = 0.95 m
Two resistors are arranged in series. RA = 6Ω and RB = 9Ω . 3V is supplied to the circuit. What is the power through resistor A?
I = V/R = 3V/15Ω
VA = IRA = (0.2A)(6Ω ) = 1.2 V
PA = IVA= (0.2A)(1.2V) = 0.24W
What is the change in temperature of a sample of 5.6 kg sample that absorbs 8,840 cal of heat from its surroundings?
EH = 8,840 cal x 4.19 J/1 cal = 37039.6 J
ΔT= EH/mc = 37039.6 J/ (5.6kg)(4200J/kgK) = 1.57 K
A tank has an energy input of 3.5 kJ. Calculate the efficiency of the tank of it exerts a force of 20 N while moving 50 m. Give answer to 3 significant figures.
Ein = 3.5 kJ Eout = Fd = 20 N x 50 m = 1000J
Eff = Eout/Ein x 100 = 1000J/3500J x 100 = 28.6%