chapter 13 : electrical systems

Question 1

what is a cell

Answer 1

a cell is an energy source for the circuit, it has a positive and negative terminal
a few cells forms a battery
cell - 1

Question 2

SI unit forr current
symbol for current

Answer 2

Ampere (A)
I

Question 3

what is a current

Answer 3

rate of flow of electric charges
electric charges = electrons

Question 4

conventional current and electron flow

Answer 4

closed circuit : electrons flow from negative to positive
HOWEVER
draw the conventional current (positive to negative) instead of electron flow

Question 5

measurement of current

Answer 5

ammeter
connected in series
positive terminal (ammeter) - positive terminal (cell)

Question 6

what is potential difference (voltage)

Answer 6

the AMT of energy needed to move a unit charge from one point to another in the electrical circuit

Question 7

SI unit and symbol for voltage

Answer 7

SI unit : volt (V)
symbol : V
to be connected in parallel,
negative (voltmeter) - negative (cell)

Question 8

what is resistance

Answer 8

the electrical component that resists flow of charges

Question 9

SI unit , symbol and formula for resistance

Answer 9

SI unit : ohm
symbol : R
potential difference ( voltage ) = resistance x voltage

Question 10

electrical conductttors and insulators resistance ability

Answer 10

electrical conductors have low resistance while electrical insulators have high resistance as electrical conductors have free moving electrons to conduct electricity but electrons in electric insulators are unable to move

Question 11

what are the 2 types of resistor

Answer 11

fixed resistor
(fixed value of resistance)
variable resistor (rheostat)
(resistance can change, used to adjust brightness of lamps etc)

Question 12

what are useful effects of electricity

Answer 12

chemical effect
heating effect
magnetic effect

Question 13

chemical effect

Answer 13

current pass thru certain chemical solutions, chemical changes take place, resulting in coating an object with a thin layer of metal (electroplating)
surgical instruments are electroplated to minimize infections

Question 14

heating effect

Answer 14

current pass thru heating element (infant incubator to maintain a warm constant temp)

Question 15

magnetic effect

Answer 15

current pass thru a coil of fire, making it an electromagnet

Question 16

what are harmful effects of electricity

Answer 16

overloading can cause electrical fire
damaged wires, damp conditions can cause electric shock

Question 17

safety devices in our household

Answer 17

fuse
a small piece of wire that will melt when the current exceeds its rating
circuit breaker
individual lever like switches, when the current flow is too large due to a faulty electrical appliance, the switched linked to the appliance trips and cuts off the current to the appliance, this prevents electric shocks

Question 18

consumption of electrical energy

Answer 18

SI unit : watt (W)
1KW=1000 W
10W = 10 per second’

electrical energy (kWh) = power (kW) x time

cost of electrical consumption = electrical energy (kWh) x electrical tariff (cents per kWh)