Energy

Question 1

do hybrid car need external electric source?

Answer 1

No

Question 2

what is the primary energy source of hybrid car?

Answer 2

100% petrol

becuase electricity is mnade by petrol also

Question 3

hybrid car’s internal engine

Answer 3

power is lower than that of conventional car

as electric motor will help

Question 4

moderator usage

Answer 4

slows down neutrons to increase rate of fission

Question 5

solar cell energy conversion

Answer 5

light energy –> electrical energy

Question 6

why solar power is renewable

Answer 6

energy comes from natural resources

Question 7

why electric vehicles need mechanical braking system

Answer 7

mechanical braking system may come into play when the regenerative braking system fails

Question 8

solar panel energy conversion

Answer 8

solar energy –> electrical energy–> chemical energy

Question 9

how to improve the absorption of energy of a solar cell

Answer 9

adhere a transparent anti-reflection film

Question 10

why the blackboard in classroom should be rough

Answer 10

reflection becomes diffuse to reduce glare

Question 11

why LED is good

Answer 11

it has a long life time and very high efficacy

Question 12

what does binding energy means

Answer 12

the energy required to separate all nucleons to infinity or separate completely

Question 13

why fuel rods are usually replaced before the time that it is used up

Answer 13

the concentration of radioactive nuclei is too low that chain reacton cannot be maintained

Question 14

use of moderator

Answer 14

slow down the fast neutron produced by fission

Question 15

use of control rod

Answer 15

to control the rate of nuclear fission by absorbing the neutrons
or for shutting down the reactor in case of emergency

Question 16

why COP > 1 does not violate the principle of conservation of energy

Answer 16

For each Joule of electrical energy consumed by the air conditioner, an amount of joule of heat is removed nor created by the air conditioner

Question 17

what is heat pump

Answer 17

a device that transfer heat against its natural direction of flow

Question 18

why incandescent lamp emit a braod range of frequency

Answer 18

the energy level of the electrons in a solid filament are numerous and closely spaced

Question 19

why filament in lamp is very thin

Answer 19

P=I^2R
and R= pl/A
when thinner then A decrease
R increase then P increase
so higher power output

Question 20

what is the function of the inert gas in the bulb

Answer 20

slows down the evaporation of the filament

or lengthen the lifetime

Question 21

why binding energy is negative

Answer 21

the attractive force between nucleons gives rise to the nuclear binding energy.
Because the collection of neutrons and protons has less energy than the same particles have when far apart, the nuclear binding energy is thus negative

Question 22

explain why we cannot stop the I-131 producing heat (undergoing decay)

Answer 22

radioactive decay is spontaneous and cannot be speed up or slow down

(eg. a decay, b decay, gamma decay)