Electrical Engineering - Energy and Power - Discussion
Discussion Forum : Energy and Power - General Questions (Q.No. 7)
7.
A 15 V source is connected across a 12 
resistor. How much energy is used in three minutes?
resistor. How much energy is used in three minutes?Discussion:
31 comments Page 1 of 4.
Fakhur said:
3 years ago
I will assume that this is not in a very hot ambient temperature nor is it sandwiched between other hot components.
In that case, good engineering practice is to use a resistor rated for at least 2x the required power dissipation.
One formula for power is I squared times R.
P = 0.025A^2 x 120 ohms = 0.075W or 75mW.
So, a resistor rated at least double that 150mW.
In that case, good engineering practice is to use a resistor rated for at least 2x the required power dissipation.
One formula for power is I squared times R.
P = 0.025A^2 x 120 ohms = 0.075W or 75mW.
So, a resistor rated at least double that 150mW.
(3)
Dhanajayaalthi said:
6 years ago
Voltage= 15v.
Resistor= 12 ohms.
POWER(P) = VI * t.
= (V*(V/R) ) * t Bcoz I= V/R
= ((V)^2 /R) *t
= ((15)^2 /12 )*(3/60) (for 3 mins)
= (225/12) * (1/20)
= 18.76 * 0.05
= 0.938 kwh.
Resistor= 12 ohms.
POWER(P) = VI * t.
= (V*(V/R) ) * t Bcoz I= V/R
= ((V)^2 /R) *t
= ((15)^2 /12 )*(3/60) (for 3 mins)
= (225/12) * (1/20)
= 18.76 * 0.05
= 0.938 kwh.
(7)
Pratap sahu said:
1 decade ago
Let
V = 15, R = 12.
So I = V/R = 15/12 = 1.25 A.
And P=V*I, So P = 15*1.25 = 18.75wh.
In 1 hour power will consume 18.75wh.
In 1 minute power will consume = 18.75/60 = 0.3125wh.
In 3 minute power will consume = 0.3125*3 = 0.9375wh.
V = 15, R = 12.
So I = V/R = 15/12 = 1.25 A.
And P=V*I, So P = 15*1.25 = 18.75wh.
In 1 hour power will consume 18.75wh.
In 1 minute power will consume = 18.75/60 = 0.3125wh.
In 3 minute power will consume = 0.3125*3 = 0.9375wh.
Ravi Purohit said:
1 decade ago
As per ohm's law,
R = V / I
I = V / R
= 15 / 12
= 1.25 A
And Power P = V * I
= 15*1.25
= 18.75 w
Given duration is 3 miniute i.e. 3 / 60 hour
Therefore, Watt-hour = 18.75 * (3 / 60) = 0.9375
R = V / I
I = V / R
= 15 / 12
= 1.25 A
And Power P = V * I
= 15*1.25
= 18.75 w
Given duration is 3 miniute i.e. 3 / 60 hour
Therefore, Watt-hour = 18.75 * (3 / 60) = 0.9375
Dhina said:
5 years ago
Energy=power *Time
J=w*s
V=15
3mins/60 = 0.05 s
R=12.
Power=I*v
I=V/R
=15/12.
I=1.25.
P=1.25*5,
P=18.75.
J= 18.75 * 0.05.
J= 0.9375.
J=w*s
V=15
3mins/60 = 0.05 s
R=12.
Power=I*v
I=V/R
=15/12.
I=1.25.
P=1.25*5,
P=18.75.
J= 18.75 * 0.05.
J= 0.9375.
(13)
BhuPavKar said:
7 years ago
WKT, P=[(I)^2] * R (Unit - Watts) --> eqn 1.
Energy = E = P * t (Unit - Watt-hour) --> eqn 2.
Given = t = 3 min; But, t in hours = (3/60) hrs.
Next, I = V/R = 15/12 = 1.25.
Sub t and I in eqn 2, we get E = 0.9375Wh.
Energy = E = P * t (Unit - Watt-hour) --> eqn 2.
Given = t = 3 min; But, t in hours = (3/60) hrs.
Next, I = V/R = 15/12 = 1.25.
Sub t and I in eqn 2, we get E = 0.9375Wh.
(4)
Minnu said:
9 years ago
P = V^2/R = (15)^2/12,
= 225/12 = 18.75,
t = 3 minutes = (3/60) Hours = 0.05 Hours,
So, ENERGY consumption in 3 minutes is, E = P * t.
= 18.75 * 0.05 = 0.9375 Wh OR make it as round figure = 0.938 Wh.
= 225/12 = 18.75,
t = 3 minutes = (3/60) Hours = 0.05 Hours,
So, ENERGY consumption in 3 minutes is, E = P * t.
= 18.75 * 0.05 = 0.9375 Wh OR make it as round figure = 0.938 Wh.
(1)
RAFI said:
1 decade ago
Energy=power*time
p=v*I
p=v*(v/R)(i=v/r)
p=Vsquare/R
=15*15/12=18.75
NOW,ENERGY IN 3MINUTES=18.75*3=56.25WATT MINUTES
ENERGY IN HOUR=18.75*0.05=0.9375WATT HOUR(3MINUTES=0.05HOUR)
ANSWER IS B
p=v*I
p=v*(v/R)(i=v/r)
p=Vsquare/R
=15*15/12=18.75
NOW,ENERGY IN 3MINUTES=18.75*3=56.25WATT MINUTES
ENERGY IN HOUR=18.75*0.05=0.9375WATT HOUR(3MINUTES=0.05HOUR)
ANSWER IS B
Mohamed Basha j said:
1 decade ago
P = V^2 / R , so P= 15^2*12 p = 18.75watts.
For 3 min = 3/60 = .05.
Used Energy = 18.75 * .05.
= 0.9375 Wh.
Answer = option B.
For 3 min = 3/60 = .05.
Used Energy = 18.75 * .05.
= 0.9375 Wh.
Answer = option B.
Hazrat Bilal Safi said:
1 decade ago
@Aramuthan. You are wrong.
P = IV;
I = V/R;
Since,
I = 15/12.
I = 1.25A.
P = 1.25*15 = 18.75.
3 minute= 3/60 hours = 0.05h.
Energy= 18.75* 0.05= 0.9375Wh.
P = IV;
I = V/R;
Since,
I = 15/12.
I = 1.25A.
P = 1.25*15 = 18.75.
3 minute= 3/60 hours = 0.05h.
Energy= 18.75* 0.05= 0.9375Wh.
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