Electrics

Question 1

Why can a charged particle sometimes attract an uncharged particle?

Answer 1

• electrostatic induction

Question 2

What is electrostatic induction?

Answer 2

• redistribution of electric charge caused by presence/influence of nearby charges

Question 3

What is matter made up of?

Answer 3

• proton, neutron, electron
• uncharged particle has equal number of protons and electrons

Question 4

Uniform Field

Answer 4

• same strength at all points
• same distance between the field lines
• between parallel plates

Question 5

Radial Field

Answer 5

• spreads out in all directions

Question 6

What is electric field strength?

Answer 6

• at a point is “force per unit charge” exerted on a stationery positive change at that point

Question 7

What type of path does a charge moving through a uniform field follow?

Answer 7

• parabolic

Question 8

convential current

Answer 8

• current goes from positive terminal to negative terminal
• same direction as positive charge flow

Question 9

electric current

Answer 9

• current goes from negative to positive terminal
• electron flow

Question 10

A current of 1 Ampere

Answer 10

• a charge of 1C passes through a point in 1 second
• 1 coulomb per second

Question 11

What is electric current?

Answer 11

• rate of flow of electric charge past a point

Question 12

elementary charge

Answer 12

• magnitude of a charge of one electron
• -1.6 * 10^-19 C

Question 13

What is potential difference between 2 points?

Answer 13

• energy given up by the unit charge as it moves from point 1 to point 2

Question 14

what is electromotive force (emf)?

Answer 14

• total work done when a unit charge goes around a complete circuit
• energy “gain” by charge from battery

Question 15

define the ohm

Answer 15

• resistance of a component when p.d. of 1 V drives a current of 1A through it

Question 16

ammeter and voltmeter

Answer 16

• ammeter is connected in series with conductor so that the “same current” flows through them
• voltmeter is connected in parallel with conductor to measure the p.d. across it

Question 17

function of a fuse

Answer 17

• to break the circuit if a fault in a appliance causes too much current to flow

Question 18

kirchoff’s first law

Answer 18

• sum of currents entering a point in a circuit is equal to the sum of currents leaving the exact same point

Question 19

kirchoff’s second law

Answer 19

• sum of emfs across a circuit is equal to the sum of p.d.s
• result of conservation of energy
• if a charge of 1 C passes through a circuit it gains energy when it passes through sources of energy (emf) and lose energy when it passes through potential differences
• basically, energy gained passing through emfs = energy lost passing through pds

Question 20

I-V characteristic graph

Answer 20

• current-voltage charcteristic
• current is directly proportional to voltage (straight line)
• resistance R dosn’t change; V/I is constant
• any component which behaves like this is an ohmic component

Question 21

Ohm’s Law

Answer 21

• for a metallic conductor at constant temperature, current is directly proportional to potential difference across its ends

Question 22

non-ohmic components

Answer 22

• semiconductor diode (like LED) for example
• resistance depends on p.d. across it; it can change
• I.V. graph is not a staight line

Question 23

electric potential difference required to stop photoelectrons completely

Answer 23

• stopping potential