Three wires enter most homes from the power pole—two “hot” wires and a third “neutral” wire. Each hot wire provides 120-volt current for conventional lights, receptacles, and appliances when paired with the neutral wire, which is normally kept at zero volts or “ground potential.” When both hot wires are used together with the neutral, they power large 240-volt appliances such as air conditioners and electric ovens. All the electric appliances stop working in a house when the main switch is put off because the electric circuit (the path where the electricity travels) gets opened. A circuit needs to be closed in order for current to flow through it and thus all electric appliances to work. Switching off the main supply involves breaking the circuit and hence the current flow through the circuit. Turning off a wall switch does not necessarily turn off the power to a fixture or receptacle; the power at the circuit breaker should be shut off. On the electrical box, we can see a row of switch. One main switch is particular unique in colour or size. This is the main switch which cuts off the supply from live and neutral wire. In rest of the switches, only the live wire is disconnected. This is an important note to take, and the same applies to the wall switches.

Correct Option: C

Three wires enter most homes from the power pole—two “hot” wires and a third “neutral” wire. Each hot wire provides 120-volt current for conventional lights, receptacles, and appliances when paired with the neutral wire, which is normally kept at zero volts or “ground potential.” When both hot wires are used together with the neutral, they power large 240-volt appliances such as air conditioners and electric ovens. All the electric appliances stop working in a house when the main switch is put off because the electric circuit (the path where the electricity travels) gets opened. A circuit needs to be closed in order for current to flow through it and thus all electric appliances to work. Switching off the main supply involves breaking the circuit and hence the current flow through the circuit. Turning off a wall switch does not necessarily turn off the power to a fixture or receptacle; the power at the circuit breaker should be shut off. On the electrical box, we can see a row of switch. One main switch is particular unique in colour or size. This is the main switch which cuts off the supply from live and neutral wire. In rest of the switches, only the live wire is disconnected. This is an important note to take, and the same applies to the wall switches.

The knot (pronounced not) is a unit of speed equal to one nautical mile (1.852 km) per hour, approximately 1.151 mph. There is no standard abbreviation but km is commonly used. The knot is a non-SI unit accepted for use with the International System of Units (SI). Worldwide, the knot is used in meteorology, and in maritime and air navigation—for example, a vessel travelling at 1 knot along a meridian travels one minute of geographic latitude in one hour. The speeds of vessels relative to the fluids in which they travel (boat speeds and air speeds) are measured in knots.

Correct Option: A

The knot (pronounced not) is a unit of speed equal to one nautical mile (1.852 km) per hour, approximately 1.151 mph. There is no standard abbreviation but km is commonly used. The knot is a non-SI unit accepted for use with the International System of Units (SI). Worldwide, the knot is used in meteorology, and in maritime and air navigation—for example, a vessel travelling at 1 knot along a meridian travels one minute of geographic latitude in one hour. The speeds of vessels relative to the fluids in which they travel (boat speeds and air speeds) are measured in knots.

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification. Physically, rectifiers take a number of forms, including vacuum tube diodes, mercury-arc valves, solid-state diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage direct current power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. As noted, detectors of radio signals serve as rectifiers.

Correct Option: C

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification. Physically, rectifiers take a number of forms, including vacuum tube diodes, mercury-arc valves, solid-state diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage direct current power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. As noted, detectors of radio signals serve as rectifiers.

Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water striders) to run on the water surface. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids. Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer. Water has the greatest surface tension, due to greater forces between the molecules of water compared to oil (mainly due to hydrogen bonding of water molecules to each other). So an oil droplet spreads over it.

Correct Option: D

Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water striders) to run on the water surface. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids. Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer. Water has the greatest surface tension, due to greater forces between the molecules of water compared to oil (mainly due to hydrogen bonding of water molecules to each other). So an oil droplet spreads over it.

Simple microscope - light microscope consisting of a short focus single convex lens is used to produce an enlarged image. The magnifying glass was invented by Roger Bacon in 1250. In the original ‘simple’ microscopes, a single light path went through the object viewed and one lens, increasing the visibility of the object by some amount (magnification). (One light path, one lens = simple microscope) Compound refers to the fact that in order to enlarge an image; a single light path passes through a series of lenses in a line. Each lens magnifies the image over the previous one. (One light path, multiple lenses = compound microscope) Usually, a modern compound microscope has multiple lenses within the eye tube, and a series of three or four objective lenses on the ‘head’ which can be rotated into place. The image produced is a two dimensional (2-D) image.

Correct Option: A

Simple microscope - light microscope consisting of a short focus single convex lens is used to produce an enlarged image. The magnifying glass was invented by Roger Bacon in 1250. In the original ‘simple’ microscopes, a single light path went through the object viewed and one lens, increasing the visibility of the object by some amount (magnification). (One light path, one lens = simple microscope) Compound refers to the fact that in order to enlarge an image; a single light path passes through a series of lenses in a line. Each lens magnifies the image over the previous one. (One light path, multiple lenses = compound microscope) Usually, a modern compound microscope has multiple lenses within the eye tube, and a series of three or four objective lenses on the ‘head’ which can be rotated into place. The image produced is a two dimensional (2-D) image.