Efficiency = (Wanted) energy out ÷ energy in × 100
Energy in = 400J
Wanted Energy out = 240J
Energy cannot be used up, only transferred, so the remaining energy is most likely to be transferred into unwanted energy (loss of energy) such as heat energy.
Efficiency = 240 ÷ 400 × 100
Efficiency = 0.6 × 100
Efficiency = 60%
Answer:
1.11 V
Explanation:
Given that the Einstein photoelectric equation states that;
KE = E - Wo
E = energy of incident photon
Wo= work function of the metal
E = hf = 6.64 x 10-34 * 6 x 1014
E = 39.84 * 10^-20 J or 3.98 * 10^-19 J
KE = 3.98 * 10^-19 J - 2.2 x 10-19J
KE = 1.78 * 10^-19J
We convert this value of KE to electron volts
KE = 1.78 * 10^-19J/1.6 x 10-19C
KE = 1.11 eV
Hence; 1.11 V will be just sufficient to stop electrons emitted by the sodium photo-plate reaching the collector plate.
Answer:
P = 0.25 W
Explanation:
Given that,
The emf of the battry, E = 2 V
The resistance of a bulb, R = 16 ohms
We need to find the power delivered to the bulb. We know that, the formula for the power delivered is given by :

So, 0.25 W power is delivered to the bulb.
Answer:
Explanation:
mg = kx
x = mg/k
x = 30(80)(9.8)/2.8e7 = 0.00084 m ≈ 1 mm