Physics

Kirchhoffs first rule – problems and solutions 1. Based on figure as shown below, if I1 = 5A, I2 = 3 A, I3 = 6 A, then I4 = ……… Solution : Kirchhoff’s first rule states that the sums of all currents entering the junction must equal the sum of all currents leaving the junction. … Read more

Transverse and longitudinal waves – problems and solutions 1. A wave is traveling down a 3-m long wire for 0.3 seconds. What is the period of the wave? Known : Time interval (t) = 0.3 seconds Wanted : Period (T) Solution : 1 wavelength = 1 crests + 1 troughs Period = 2 x 0.1 … Read more

Buoyant force – problems and solutions 1. A block of wood with length = 2.5 m, width = 0.5 m and height = 0.4 m. The density of water is 1000 kg/m3. If the block is placed in the water, what is the buoyant force… Acceleration due to gravity is 10 N/kg. Known : Volume … Read more

25 Electric energy – problems and solutions 1. A 220 V – 5 A electric lamp is used for 30 minutes. How much energy does it require? Solution : Voltage (V) = 220 Volt Electric current (I) = 5 Ampere Time (t) = 30 minutes = 30 x 60 seconds = 1800 seconds Electric power … Read more

28 Electric power – problems and solutions 1. Calculate the electric current of a 10 Watt lamp designed for 12 Volt. Known : Power (P) = 10 Watt Voltage (V) = 220 Volt Wanted : Electric current Solution : Lamp power = 10 Watt = 10 Joule/second The equation below shows the relation between the … Read more

25 Carnot engine (application of the second law of thermodynamics) – problems and solutions 1. An engine operates between 1200 Kelvin and 300 Kelvin. What is the efficiency of this engine? Known : High temperature (TH) = 1200 K Low temperature (TL) = 300 K Wanted: Efficiency (e) Solution : 2. An engine operates between … Read more

30 Heat engine (application of the second law of thermodynamics) – problems and solutions 1. Heat input QH = 3000 Joule and heat output QL = 1000 Joule. What is the efficiency of the heat engine? Known : Heat input (QH) = 3000 Joule Heat output (QL) = 1000 Joule Work done by the engine … Read more

30 Isobaric thermodynamics processes – problems and solutions 1. PV diagram below shows an ideal gas undergoes an isobaric process. Calculate the work is done by the gas in the process AB. Known : Pressure (P) = 5 x 105 N/m2 Initial volume (V1) = 2 m3 Final volume (V2) = 6 m3 Wanted : … Read more

30 Isochoric thermodynamics processes – problems and solutions 1. PV diagram below shows an ideal gas undergoes an isochoric process. Calculate the work is done by the gas in the process AB. Solution : Process AB is an isochoric process (constant volume). The volume is constant so that no work is done by the gas. … Read more

30 Isothermal thermodynamic processes – problems and solutions 1. PV diagram below shows an ideal gas undergoes an isothermal process. Calculate the work is done by the gas in the process AB. Solution Work done by a gas is equal to the area under the PV curve AB = triangle area + rectangle area W … Read more