Answer:

Explanation:
Given:
Capacitance, C = 85 pF = 85 × 10⁻¹² F
Resistance, R = 75 MΩ = 75×10⁶Ω
Charge in capacitor at any time 't' is given as:

where, 
Q₀ = Maximum charge = CE
E = Initial voltage
t = time
also, Q = CV 
V= Final voltage = 90% of E = 0.9E
thus, we have

or

or

taking log both sides, we get

or

or

or

 
        
             
        
        
        
Answer:
Make sure everything is organized have a planner it can help
Get rid of all distractions
Listen to music if it helps you concentrate
Have your notes
Being willing to stay focus on what you are doing 
Understand what you are doing
And most off all Be Happy and Remain Calm : )
 
        
                    
             
        
        
        
Answer:
Explanation:
mass of 1 L water = 1 kg . 
200⁰F = (200 - 32) x 5 / 9 = 93.33⁰C .
260.928 K = 260.928 - 273 = - 12.072⁰C . 
water is at higher temperature . 
Let the equilibrium temperature be t . 
Heat lost by water = mass x specific heat x  fall of temperature 
= 1 x 4.2 x 10³ x ( 93.33 - t ) 
Heat gained by copper 
= .25 x .385 x 10³ x ( t +  12.072 ) 
Heat lost = heat gained 
 1 x 4.2 x 10³ x ( 93.33 - t ) = .25 x .385 x 10³ x ( t +  12.072 ) 
 93.33 - t = .0229 ( t + 12.072)
93.33 - t = .0229 t + .276 
93.054 = 1.0229 t 
t = 90.97⁰C .