Charge Static electricity can be generated by rubbing a cloth on a plastic rod. What happens is CHARGE is transferred from one to the other. Charged rods interact one with the other

Charge Charge can be negative or positive. Similar charges repel, opposite charges attract.

Charge Charge has the symbol Q. When we say a body is uncharged, we mean it has equal quantities of positive and negative charge. Charge has the symbol Q. The SI unit of charge is the coulomb (C) 1 C= 1 ampere *1 sec= 1 As.

Charge Charge has symbol Q. SI unit: coulomb (C) 1 C = 1 As Static electricity can be generated by rubbing a cloth on a plastic rod. What happens is CHARGE is transferred from one to the other. Charge can be negative or positive. Similar charges repel, opposite charges attract. When we say a body is uncharged, we mean it has equal quantities of positive and negative charge. Charge has symbol Q. SI unit: coulomb (C) 1 C = 1 As

Origin of Charge The electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction.

Origin of Charge Atoms in matter comprise three types of particles: electrons (electrically negative). protons (electrically positive). neutrons (electrically neutral). Different atoms have different number of protons, neutrons and electrons

Origin of Charge Anyone happen to know? Atoms in matter comprise three types of particles: electrons (electrically negative). protons (electrically positive). neutrons (electrically neutral). The electron (symbol: e−) is a subatomic particle with a negative elementary electric charge. Electron Mass = 9.11×10−31 kg Electron charge = −1.6×10−19 C Anyone happen to know?

Origin of Charge Anyone happen to know? Atoms in matter comprise three types of particles: electrons (electrically negative). protons (electrically positive). neutrons (electrically neutral). The proton is a subatomic particle with the symbol p+ and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom. Proton Mass = 1.67×10−27 kg Proton charge = +1.6×10−19 C Anyone happen to know?

Origin of Charge Atoms in matter comprise three types of particles: electrons (electrically negative). protons (electrically positive). neutrons (electrically neutral). The neutron is a subatomic particle which has the symbol n0, no electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons.

Origin of Charge Electrons Protons and neutrons The protons and neutrons form a positive nucleus that the electrons orbit. Different isotopes of the same chemical element differs by the number of neutrons .

Origin of Charge The friction in the rubbing causes electrons to be transferred to the plastic, leaving behind a net positive charge - ions.

Origin of Charge Atoms in matter comprise three types of particles: electrons (electrically negative). protons (electrically positive). neutrons (electrically neutral). The protons and neutrons form a positive nucleus that the electrons orbit. The friction in the rubbing causes electrons to be transferred to the plastic, leaving behind a net positive charge - ions.

Conductors and Insulators Some materials allow electrical charge to pass through them easily - called CONDUCTORS. Conductors such as metals have free electrons that can carry the charge from one place to another. Such materials are used for wires.

Conductors and Insulators Some materials do not allow electrical charge to pass – called INSULATORS. In insulators, the electrons are bound in place. Insulating materials are used for industrial insulators

Conductors and Insulators Semiconductors are insulating materials that may be made partially conducting by adding impurities. Very important for electronics (diodes, transistors etc.) In semiconductors, electrons stay near one atom for a long time and seldom jump from one atom to the other.

Conductors and Insulators Some materials allow electrical charge to pass through them easily - called CONDUCTORS. Some do not - INSULATORS. Conductors such as metals have free electrons that can carry the charge from one place to another. In insulators, the electrons are bound in place. Semiconductors are insulating materials that may be made partially conducting by adding impurities.

Field and Potential Similar charges repel, opposite charges attract. How to describe this effect? Coulomb’s Law is a law of physics describing the electrostatic interaction between electrically charged particles. It was first published in 1785 by French physicist Charles Augustin de Coulomb.

Field and Potential Coulomb’s Law is a law of physics describing the electrostatic interaction between electrically charged particles.

Field and Potential Coulomb’s Law is a law of physics describing the electrostatic interaction between electrically charged particles.

Field and Potential Coulomb’s Law is a law of physics describing the electrostatic interaction between electrically charged particles. Interaction of opposite charges reminds of the interaction of two masses.

Field and Potential U= mgh, U=m(GM/r), Gravitational potential energy: the higher the altitude of an object the larger the potential energy U= mgh, where g is the gravitational acceleration (9.8 m/s2), h is distance above ground (above the sea level). If the distance to the ground is large, we need to take into account that g depends on this distance and potential energy becomes: U=m(GM/r), where G is the gravitational constant, M is the Earth mass, r is the distance to the Earth centre. We replace “gh” by the gravitational potential “V=GM/r “

Field and Potential Do we have a potential energy for electric charges? - Yes! Compare electric and gravitational interactions: Gravitational Electrical Force, F F=GmM/r2 F=ke qQ/r2 Potential energy, U U= mgh, for small h , or U=GMm/r U=ke qQ/r Potential, V (potential energy per unit charge or mass) V = U/m=GM/r V= U/q=ke Q/r

Field and Potential The electrostatic potential is electrostatic energy of a 1C charge. To get a potential energy of a charge “q” we have to multiply the electrostatic potential by “q”: U=qV. Electrostatic potential of a point charge Q is constant when going along circle line centred in the charge. This is similar to the gravitational potential energy: The gravitational energy is the same for all points with the same distance from the ground. We introduce potential energy per charge. What about the electric force per charge (force acting on a 1C) charge? Q Potential at these two points is the same

Field and Potential What is the electric field? If we have two charges they interact via Coulomb force. Do we have anything if we have only one charge “q”? If we imagine a “test” charge of 1C, it would interact with our charge “q” with the force: This “imaginary” force, E, exists everywhere and it’s called the electric field. It could be drawn as a vector (“an arrowed line”) at each spatial point. Q

Field and Potential The electric field intensity is defined as the force per unit positive charge that would be experienced by a stationary point charge, or "test charge", at a given location. So we have a vector (arrowed line) E in each spatial point. “Connecting” ends and heads of vectors we can draw “electric field lines”

Field and Potential Electric fields for simple systems One positive charge: electric lines go away from the charge. One negative charge: electric lines go into the charge. One positive and one negative charges: electric field lines start from the centre of positive charge and go into negative charge. Two positive charges. Lines start from both charges and “repel” lines from the other charge.

Field and Potential Q Q

Origin of Charge Atoms in matter comprise three particles: electrons (electrically negative). protons (electrically positive). neutrons (electrically neutral). The electron (symbol: e−) is a subatomic particle with a negative elementary electric charge. It has no known substructure; in other words, it is generally thought to be an elementary particle. The antiparticle of the electron is the positron with positive charge and the same mass. Electron Mass = 9.1×10−31 kg Electron charge = −1.6×10−19 C

Origin of Charge Atoms in matter comprise three particles: electrons (electrically negative). protons (electrically positive). neutrons (electrically neutral). The proton is a subatomic particle with the symbol p+ and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom. The proton particle is composed of three fundamental particles: two up quarks and one down quark. The antiparticle of the proton is the antiproton. Proton Mass = 1.67×10−27 kg Proton charge = +1.6×10−19 C

Origin of Charge Atoms in matter comprise three particles: electrons (electrically negative). protons (electrically positive). neutrons (electrically neutral). The proton is a subatomic particle with the symbol p+ and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom. The proton particle is composed of three fundamental particles: two up quarks and one down quark. The antiparticle of the proton is the antiproton. Proton Mass = 1.67×10−27 kg Proton charge = +1.6×10−19 C

Field and Potential Similar charges repel, opposite charges attract. How to describe this effect? Coulomb’s Law is a law of physics describing the electrostatic interaction between electrically charged particles. “The magnitude of the Electrostatics force of interaction between two charges is directly proportional to the multiplication of the magnitudes of charges and inversely proportional to the square of the distances between them." It was first published in 1785 by French physicist Charles Augustin de Coulomb.