How do electrical charges behave Topic 3.2

Topic 3.2 Key Concepts Electrons carry a negative charge, and protons carry a positive charge Opposite charges attract each other, and like charges repel each other

Concept 1: Electrons carry a negative charge; Protons carry a positive charge - can be rubbed off a material The charges of Surround the - left behind when negative charges are rubbed off a material Part of the of atoms Held firmly in place, unlike electrons, so they cannot be rubbed off Negative charge electrons nucleus Positive charge protons nucleus

Negative & Positive charges When electrons are rubbed off a material, the material becomes charged That material that electrons becomes charged Charging material by rubbing is called Whether a material gains or loses electrons depends on the combination of materials Negative & Positive charges positively charge gains negatively charging by friction

Electrically neutral & electrically charged materials - before 2 materials are rubbed together, they have numbers of positively charged protons and negatively charged electrons The positive and negative charges cancel out, leaving the material - if electrons are rubbed off, the protons stay behind, making the material The material gaining electrons is also electrically charged Being electrically charged means there is an number of positive and negative charges Uncharged materials equal neutrally charged Charged materials positively charged unequal

Explain the relationships among negative charges, positive charges, electrons, and protons. Describe what sometimes happens in terms of charges when you rub 2 different types of materials together. Discussion questions

Concept 2: opposite charges attract & like charges repel – summarizes the properties of charges (how charges interact with each other) 1) Every negative charge attracts every positive 2) Every negative charge repels every other negative charge; every positive charge repels every other positive charge Law of Electric Charge Opposite charges attract each other Like charges repel each other Phet activity

Concept 2: opposite charges attract & like charges repel Why does a charged balloon stick to an electrically neutral wall? when a object (balloon) is brought near a object (wall), the in the neutral object do not come off Negative charges in the wall are from the surface by the negative charges on the balloon Positive ends of the molecules in the wall are to the negative charges on the balloon This attraction is strong enough to hold the balloon to the wall charged neutral electrons pushed away Phet activity attracted

Discussion questions State the law of electric charge. Make a labeled sketch, including charges, to explain why a stream of neutral water bends towards a positively charged comb Discussion questions