Simply put, electric appliance can be very simple with just a live wire bring in the current and a neutral wire to bring the current out. The appliance can just work like this forever (without the hassle of having earth wire, fuse etc), provided there is no electric fault developed. Both the earth wire and the fuse are safety features to protect the user and the appliance respectively . Take a look at the video below to understand the rationale. Recall these notes given:

Answer: Option D

There are 3 scenarios with slight variations. Calculate the force F needed to pull the block up the inclined plane. View the video below to understand how to solve these types of question.

Though slinky coil is commonly used to demonstrate transverse and longitudinal waves, you must not quote it as an example for either of the waves. Transverse waves are waves in which the direction of the wave is perpendicular to the direction of the vibration of the particles. Examples are light wave, water wave or all the waves in the electromagnetic spectrum (which light is one of the waves. Longitudinal waves are waves in which the direction of the wave is parallel to the direction of the vibration of the particles.  Example is sound wave (inludes ultrasound and infrasound) Transverse Waves (slinky coil) Longitudinal Waves (slinky coil) Transverse Waves Animation Longitudinal Waves Animation

When an object is oscillating or vibrating in a wave motion , the speed of the object varies along the path. In this video, there are 3 examples of vibrating object. 1) Mass vibrating vertically from a spring 2) Pendulum bob oscillating 3) A particle vibrating up and down on a transverse wave In general, when the object is at the extreme ends of the oscillation or vibration , it is momentarily at rest . Hence its KE at these points is minimum or 0 J . And in the middle that is where the object is travelling the fastest , hence the KE is the maximum .

1. Converging lens (convex lens) Converging lens, also known as convex lens,  is thicker at the centre. Below shows some examples. In O-level, we learned about symmetrical converging lens. i.e. the curvature of the lens are the same on both sides. As light rays pass through the converging lens, the rays come closer together . Take note that the bending of light, refraction, takes place on the air-glass boundaries on both sides of the lens (as shown above). But for easy drawing, we draw the bending at the imaginary centre vertical which passes through the optical centre as shown below. If the parallel rays are at an angle, the light rays will converge on a point P which lies on the focal plane. 2. The 3 Rays The following 3 rays are important for us to construct the ray diagram and locate the image. We always draw these 3 rays as they have rules to follow, hence guiding us in our drawing. Refer to the video below for better understanding of the 3 rays. 3. The 4 Key Scenarios Depending on the distance of the object to the centre of the lens (object distance u), the kind of image you get varies. Refer to the video below for the better understanding of how the various images are formed. 3. The Pattern Besides knowing the 4 key scenarios, it is important to know how the image behaves as the object is moved towards the lens. In general, as the object (starting from a distance of >2f) moves closer to the lens, the image will move further away from the lens and the size of the image becomes bigger. But when the object is within a focal length, as it moves closer to the lens, the virtual image moves closer to the lens and it becomes smaller compared to the image previously. But the virtual image is always bigger than the object. Refer to the video for better visualisation and understanding.

Drawing ray diagrams for converging lens come in many forms. But the basic concepts needed are the 3 rays (which have rules to follow) to locate the image. The following ray diagrams for the 4 scenarios must be learned well, together with the respective image characteristics and applications. With the basic concepts learned, when questions are asked in different ways, you should be able to draw the ray diagrams. Refer to some different ray diagram questions below and their video tutorials. Example A Example B Example C Example D Example E Example F Example G Example H Example I Example J

A pin in the beaker of water appears higher than its actual position due to refraction of light. In this experiment, you have to adjust the pin at the cork to a suitable height, such that the pin and the image of the pin inside the beaker of water is aligned and that ‘pins at position of no parallax’ position. The video below guides you in adjusting the height of the pins to locate correct height.

Solutions: Option B You can view the video tutorial here or the written solutions below.

Note: Non-uniform plank means the CG of the plank is not at its centre a) Find the weight of the boy. b) How far is the centre of gravity of the plank from point A? Solutions: a) 300 N and b) 6.67 m Click on the video tutorial if you can’t derive the 2 equations.