Answer:
The current needed to transmit Power of 4 W is 28.47 A
Solution:
As per the question:
Length of the antenna, 
Frequency, 
Power transmitted, 
Now,
For a monopole antenna:
where
= wavelength transmitted by the antenna
c = speed of light in vacuum
Now,
Since, the value of >> 
thus the monopole is a Hertian monopole.
The resistance is calculated as:
Now, the current I is given by:
Answer: 8.1 x 10^24
Explanation:
I(t) = (0.6 A) e^(-t/6 hr)
I'll leave out units for neatness: I(t) = 0.6e^(-t/6)
If t is in seconds then since 1hr = 3600s: I(t) = 0.6e^(-t/(6 x 3600) ).
For neatness let k = 1/(6x3600) = 4.63x10^-5, then:
I(t) = 0.6e^(-kt)
Providing t is in seconds, total charge Q in coulombs is
Q= ∫ I(t).dt evaluated from t=0 to t=∞.
Q = ∫(0.6e^(-kt)
= (0.6/-k)e^(-kt) evaluated from t=0 to t=∞.
= -(0.6/k)[e^-∞ - e^-0]
= -0.6/k[0 - 1]
= 0.6/k
= 0.6/(4.63x10^-5)
= 12958 C
Since the magnitude of the charge on an electron = 1.6x10⁻¹⁹ C, the number of electrons is 12958/(1.6x10^-19) = 8.1x10^24 to two significant figures.
Answer:
The group of light rays is reflected back towards the focal point thereby producing a magnifying effect.
Explanation:
:<span> </span><span>30.50 km/h = 30.50^3 m / 3600s = 8.47 m/s
At the top of the circle the centripetal force (mv²/R) comes from the car's weight (mg)
So, the net downward force from the car (Fn) = (weight - centripetal force) .. and by reaction this is the upward force provided by the road ..
Fn = mg - mv²/R
Fn = m(g - v²/R) .. .. 1800kg (9.80 - 8.47²/20.20) .. .. .. ►Fn = 11 247 N (upwards)
(b)
When the car's speed is such that all the weight is needed for the centripetal force .. then the net downward force (Fn), and the reaction from the road, becomes zero.
ie .. mg = mv²/R .. .. v² = Rg .. .. 20.20m x 9.80 = 198.0(m/s)²
►v = √198 = 14.0 m/s</span>
Answer:
7.894 Hours.
Explanation:
Based on information number hours that this battery will last with give load has mathematical relation of.
with load 60A t = 1h, 30A t = 2h so on and forth.
two head lights draw total current of 2x3.8A = 7.6A.
putting this in above relation gives.
.
That is how long will it be before battery is dead.
