Charging by Contact

Charging By Contact

Neutral objects can becomes charged through direct contact in

2 common methods:

When two different materials are rubbed together, electrons from one material are transferred to the other. This is because some materials hold on their electrons more strongly than others.

1. Charging By Friction

+---

-+ +

+

++ +

++

++

+++

-----

++

+

-

- - -

-+

+

--

-

--

Before Rubbing

For example, when you rub a balloon on your hair, the electrons in your hair are transferred to the rubber in the balloon, because the rubber holds onto electrons more strongly than hair does.

When two different materials are rubbed together, electrons from one material are transferred to the other. This is because some materials hold onto their electrons more strongly than others.

1. Charging By Friction

+-The balloon

becomesnegative.

The hairbecomespositive.

--

------+ +

+

++ +

++

++

+++

-----

++

+

-

- - -

-+

+

After Rubbing

For example, when you rub a balloon on your hair, the electrons in your hair are transferred to the rubber in the balloon, because the rubber holds onto electrons more strongly than hair does.

When two different materials are rubbed together, electrons from one material are transferred to the other. This is because some materials hold onto their electrons more strongly than others.

1. Charging By Friction

What happens when you rub materials that are the same together?

NOTHING!

For example, when you rub a balloon on your hair, the electrons in your hair are transferred to the rubber in the balloon, because the rubber holds onto electrons more strongly than hair does.

When two different materials are rubbed together, electrons from one material are transferred to the other. This is because some materials hold onto their electrons more strongly than others.

1. Charging By Friction

Once an object is charged it can pass that charge onto another object by contact.

Charged balloon makes contact with the electroscope.

-- - ---------

--

-

-

-

----

-+ +

+

++

++

+

+

+

+

+

-

-

-- -

neutral electroscope

2. Charging By Conduction

-+-

--

-- -

-

Charged balloon makes contact with the electroscope.

Electrons move from balloon to

the electroscope.

The leaves of the electroscope repel

each other.

Once an object is charged it can pass that charge onto another object by contact. The charge remains even after the object lose contact.

-- - -----

-

----

-+ +

+

++

++

- +

+

+

+

-

-

- -

charged electroscope

2. Charging By Conduction

-+-

--

-- -

-Electrons move from balloon to

the electroscope.

The leaves of the electroscope repel

each other.

Once an object is charged it can pass that charge onto another object by contact. The charge remains even after the objects lose contact.

The electroscope remains charged after contact.

Once an object is charged it can pass that charge onto another object by contact. The charge remains even after the object lose contact.

+

+

+

+

-

-

- -

charged electroscope

2. Charging By Conduction

GroundingCharged objects can cause a shock if touched. If electrons are allowed to build up in an object, when they do find a path to the ground so many of them move that they can arc through the air as a spark. To prevent gas pumps from developing a dangerous charge, all parts of the pump are well grounded by conductors (wires), so that electrons always have an easy path to the ground.

Charged objects can cause a shock if touched. If electrons are allowed to build up in an object, when they do find a path to the ground so many of them move that they can arc through the air as a spark. To prevent gas pumps from developing a dangerous charge, all parts of the pump are well grounded by conductors (wires), so that electrons always have an easy path to the ground.

Charged objects can cause a shock if touched. If electrons are allowed to build up in an object, when they do find a path to the ground so many of them move that they can arc through the air as a spark. To prevent gas pumps from developing a dangerous charge, all parts of the pump are well grounded by conductors (wires), so that electrons always have an easy path to the ground.

Walking acrossthe carpet in

socks can causeyou to become

charged.

Groundingprevents the

build up ofcharge.

Using static charges

Static electricity is actually useful! Who knew!

Have you even used a can of spray paint?

If you have you know that not all of the paint goes where you want it to. It sprays into the air and onto surrounding objects.

Electrostatic paint sprayers

To reduce the amount of paint wasted, electrostatic paint sprayers are used.

The paint is given a charge as it leaves the nozzle of the sprayer while the object to be painted is given an opposite charge.

ELECTRON AFFINITY

The tendency of a substance to hold on to its electrons is called electron affinity.

Electrostatic Series: a list of materials arranged in order of their tendency to gain electrons

Tend to lose electrons

Tend to gain electrons

(+)human hands (dry)

glasshuman hair

nyloncat fur

silkcottonsteelwoodamberebonite

plastic wrapTeflon

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