Grade 4 Science Practice Test: Electric Circuits, Conductors and Insulators

Electricity needs a closed path that leaves one end of the battery, goes through the bulb and returns to the other end. With one wire, or both wires on the same end, the loop is not complete.

Metals such as copper let electricity flow easily, which is why wires are made of copper. Rubber, wood and plastic are insulators.

Plastic does not let electricity pass, so the covering protects people from touching the current. It does not store or speed up electricity.

Opening a switch makes a gap in the circuit. Electricity cannot cross the gap, so the bulb turns off even though the battery still has energy.

In a single-loop circuit, called a series circuit, all the current goes through every bulb. A burned-out bulb breaks the loop, so both go dark.

Separate paths, called parallel circuits, let each lamp be switched or fail on its own. The other lamps keep their own complete loops.

A bulb gives off light, and it also gets warm. The battery is where the energy was stored in chemical form before it became electrical energy.

The bulb lights only when the object lets electricity cross the gap. Foil, a metal, conducts; cardboard does not.

Tap water has dissolved substances that let electricity flow through it. Wet skin makes it easier for current to reach your body, which can cause a dangerous shock.

A motor turns electrical energy into motion, so the fan blades spin. A little energy also becomes sound and heat, but motion is the main job.