4th Gr Science Ch 1 Lesson 3

What is a circuit breaker and what does it do?

A circuit breaker is a switch. If too much current flows, the circuit breaker "trips" and the switch shuts off the circuit. The switch must be reset before the circuit will work again. If a circuit breaker trips, too many devices on that circuit are being used at the same time.

In a parallel circuit, why don't all of the lights go out if one bulb in a string of lights goes out.

A parallel circuit has two or more paths through which electric charges may flow. Electric charges can flow through any of the pathways on the circuit. Even if the circuit in one of the loops is broken, the current will still flow through all of the other loops.

Describe a parallel circuit.

A parallel circuit has two or more paths through which electric charges may flow. The main path or loop leaves from and returns to the power source. Smaller loops branch off from the main loop and then connect back to it. Electric charges can flow through any of the pathways on the circuit. If the circuit in one of the loops is broken, the current will still flow through all of the other loops. A battery as the energy source Wires and metal clips to connect the circuit (conductor) A switch Branch points Light bulbs (resistor)

One bulb burns out in a string of lights but the other bulbs are still lit. What kind of circuit is this?

A parallel circuit.

How thick should an extension cord be?

An extension cord should be at least as thick as the appliance cord to which it connects. Using too thin an extension cord is a fire hazard because thinner wires have greater resistance.

Name another advantage of a parallel circuit.

Appliances use different amount of electricity. A radio or clock uses only a small amount of current. A space heater, iron, or toaster uses much more current. Each branch in a parallel circuit takes only as much current as the resistors on that branch need. In a series circuit, the current is equal in all the resistors.

Parallel circuit

Electric charges can flow in two or more paths.

What could cause none of the bulbs in a parallel circuit to light?

If all of the paths were broken or the switch was open or there was no energy source.

Why are parallel circuits used in homes and schools?

If one path is broken, the others still work. If lights are connected in a parallel circuit, you can turn each light off or on without affecting the others. This makes parallel circuits more practical than series circuits in homes, schools, and other buildings.

Explain the difference between a series circuit and a parallel circuit.

In a series circuit, electric charge can only flow through one path. A break in the path will stop the current from flowing. For example, if one bulb on a string of lights burns out on a series circuit then none of the lights will light up. In a parallel circuit, electric charge can flow in two or more paths. A break in one path will only stop the current from flowing in just that path and the current can still flow along the other path or paths. For example, if one bulb on a string of lights burns out on a parallel circuit, the rest of the bulbs will still light up.

In a parallel circuit, if one bulb is burnt out what does it do to that particular branch or path?

It opens that branch or breaks that path so that electric current can not flow through that particular path. However, the current can still flow through the other path(s).

Name some examples of good conductors of electricity?

Metal, water, and salt water. The fluids in your body are slightly salty, so you should never touch a bare wire!

What material is usually used to insulate copper electrical wires?

Plastic or rubber insulation.

What is the purpose of a fuse and how does it work?

Some electrical circuits have fuses to limit the flow of current. If too much current flows, a thin metal strip in the fuse melts. This breaks the circuit and prevents damage that too much current might cause. After the strip melts, the fuse must be replaced.

Why is it important for wires in a circuit to be insulated?

The insulation prevents your body from directly touching the wires.

What is the purpose of a plug with three prongs?

The round third prong is not always part of the circuit. If too much current flows to electrical equipment, the third prong returns the extra current to the ground. The ground can absorb it safely.

Which has greater resistance, thinner or thicker wires?

Thinner wires have greater resistance. So using too thin an extension cord is a fire hazard.

Where do electrical charges always flow?

Through the path with least resistance.

True or False Equipment or appliances that use large amounts of electricity need heavy-duty extension cords.

True

True or false In a parallel circuit, the current can be switched off in one branch and still flow through the other branches.

True

True or false Parallel circuits have more than one branch.

True

When does a short circuit occur?

When current follows a path other than the path meant for its flow. Short circuits often happen when a frayed or damaged wire touches a good conductor, such as metal or water.