7. Make up the questions off all types to the text (part1 and 2).

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Text b switches

In its simplest form, a switch is nothing but an ‘on/off’ device capable of closing and opening a circuit. Switches come in a wide variety of configurations. Some are seemingly complex in operation but their basic function is to turn equipment on and off.

Most switches are normally open, meaning when they’re relaxed, the circuit is open, or disconnected. In fact, some switches are spring-loaded to return automatically to the OFF position when you remove your finger from the switch. These are called momentary-on or momentary-contact switches. Most momentary-on switches are operated by a push button.

Some switches are made with built-in circuit protection in the form of a circuit breaker or fuse. Aftermarket switches are more likely than OEM switches to have this kind of protection, because the aftermarket switch is often used to control an accessory circuit added to the car by the owner.

The built-in fuse or breaker does away with the need to find a vacant slot in the car's fuse panel. However, if the switch you're using has no built-in circuit protection and there's no place in the fuse panel to add another, use an in-line fuse, i.e. simply place a fuse and fuse holder wired into the circuit between the load and the power source.

OEM switches usually don't have built-in circuit protection because most original circuits route through the car's fuse panel. One notable exception, particularly in American-built cars, is the

Черкаський політехнічний технікум

Тексти та завдання для ІІІ курсу спеціальності ЕА

Підготувала викладач Кудрява О.В.

headlamp switch — instead of using a fuse in the fuse panel, the switch contains a self-resetting circuit breaker.

Switches can be categorized by their electrical function, or how the switch actually works. Within each category, you may find several different kinds of switch actuators.

Single-pole, single-throw is the simplest kind of switch, with only two positions — ON and OFF. It's often referred to in parts catalogs by the initials SPST. Contrary to a popular misconception, the pole does not refer to the actuator, but the movable element inside the switch that makes and breaks the circuit. In most switches, you can't even see the pole unless you remove the housing.

Push-button-operated SPST switches turn the circuit ‘on’ when pushed, and ‘off’ when released. This is the most common form of momentary-on switch, which is the kind of switch you'd use on your house for the doorbell. Race-car starter buttons are another example. Also, a switch that activates a windshield-washer pump is of this type. Another type of push-button switch turns the circuit on with the first push and off with a second push. You'll occasionally find rotary SPST switches operated by a knob, but they’re not common in cars.