Solutions: Option B Whatever that goes in has to come out. With this basic concept, you will be able to solve this question easily. Ignoring the unknown branch, Total current going into O = 8A + 6A = 14A Total current going out of O = 12A + 4A = 16A Hence in order to be equal, 2A must be flowing in direction PO. Hence answer is B.

Based on individual calculations, the highest effective resistance will only be achieved if the junctions are connected at Q and S.

Density is the mass per unit volume . Common units for density are g/cm3 or kg/m3 . SI unit is kg/m3 . Density of a pure substance is fixed, regardless of it’s size! Floating and Sinking A denser (heavier) substance will sink in liquid which is less denser (lighter). A less dense (lighter) substance will float in a liquid which is denser . If substance has the same density as the liquid, it will be suspended in the liquid.

For Combined Science Physics Olevel, when constructing vector diagram, a method called  Parallelogram Method is commonly used. Parallelogram Method is used when 2 forces are known , and the resultant (net) force R , can be found. Below show 5 different variations of questions when can be solved by using Parallelogram Method: (A) Body has acceleration , forces are unbalanced , there is a resultant force R (Newton’s 2nd law) (B) Body at rest , all forces are balanced , there is no resultant force R (Newton’s 1st law) (C) Body moving at constant velocity , all forces are balanced , there is n o resultant force (Newton’s 1st law) (D) Finding unknown force (with  resultant force R  + another known force are given ) (E) Vector diagram is applicable to all vector quantities (with magnitude and direction). Not just for forces.

Pressure of a fixed mass of gas, P, is inversely proportional to the volume of the gas, V, when the temperature is held constant. P inversely proportional to V P = k/V , where k is a constant. PV = k With these concepts, you should be able to sketch the various graph. Do not memorise them. Use your concepts from Maths to help you to recall instead.

Double-insulated appliances are common around us. The air purifiers in our classroom are one good example. In these appliances, only two wires are needed, namely Live and Neutral wires . Earth wire is not required as the casing is made of insulator like plastic for this case. The classic air purifier in our classroom The “double squares” symbol means that this appliance is double-insulated. As you see, the earth wire is not required.

Transverse waves  are waves in which the  direction of the wave  is  perpendicular  to the direction of the vibration . e.g Light, water, and any waves in the electromagnetic spectrum Longitudinal waves  are waves in which the  direction of the wave  is  parallel  to the  direction of the vibration . e.g Sound (includes ultrasound or infrasound) Wave equation: V = fλ  In the videos below, the speed of wave is constant. Hence frequency is inversely proportional to wavelength.  [f increases, λ decreases, and vice versa]

Reflection of light using a mirror Refraction of light using various shaped optical mediums Total Internal Reflection (TIR) using a semi-circular perspex For Total Internal Reflection (TIR) to occur: 1) angle of incidence i is greater than the critical angle c 2) the light is travelling from an optically denser medium towards a less dense medium

If the circuit is open, i.e. there two ends of the solenoid is open, there is induced emf produced, but no induced current produced. That is why the magnet can fall through normal with free fall acceleration 10 m/s2. Only when the circuit is closed, there is an induced current flowing through. According to Lenz's law, the direction of the induced current is such that the magnetic effect opposses the change producing it, hence there is a repulsion force when the magnet is falling through the solenoid.