Answer:
a. 5 batteries b. 1050 mAh
Explanation:
Here is the complete question
A student project is required to be portable and hand held. It requires 6 V DC power at a current of 150 mA. The batteries for the power supply must last for a minimum of 7 hours of continuous operation. NiMH rechargeable batteries in AA size are to be used. A) How many batteries are needed? B) What mAh capacity should the batteries have?
Solution
A) How many batteries are needed?
Since the nominal voltage for a single NiMH battery is 1.2 V per battery and we require 6V DC power, we combine the batteries in series to obtain a total voltage of 6 V. The number of batteries required, n = total voltage/voltage per cell = 6V/1.2V per battery = 5 batteries
So, the number of batteries needed is 5.
B) What mAh capacity should the batteries have?
Since the batteries are in series, they would each deliver a current of 150 mA. Since we require a current of 150 mA for 7 hours, the number of milliampere-hours capacity mAh of batteries required is Q = It where I = current = 150 mA and t = time = 7 hours.
So, Q = It = 150 mA × 7 h = 1050 mAh.
So, the batteries should have a mAh of 1050 mAh
Answer:
- 6.48 J K⁻¹
Explanation:
Temperature of gas = 20°C
= 273 +20 = 293 K.
As temperature is fixed , there will be no change in gas internal energy
Δ E = 0
From the relation
Δ Q = Δ E+ Δ W
Work done on the gas is 1.9 x 10³
Δ W = - 1.9 x 10³ J
Δ Q = - 1.9 x 10³ J
Δ S = Δ Q / T
=
= - 6.48 J K⁻¹
Radiation can pass through any phase of matter.
Examples:
Light, radio, heat, and X-rays, all pass through glass (solid),
water (liquid), and air (gas) very easily.
(Moreover, I would be remiss if I failed to point out in addition that
microwave radiation passes through meatloaf and coffee with only
partial attenuation due to absorption.)
Answer:
16
Explanation:
The atomic mass of an element is defined as the average of the isotopic masses, weighted according to the naturally occurring abundances of the isotopes of the element. Although oxygen has nine isotopes with mass numbers ranging from 13 to 21, oxygen-13, oxygen-14 and oxygen-15 are not naturally occurring isotopes. So, we do not need to include them when we calculate the relative atomic mass of oxygen.