Click to Chat

1800-2000-838

+91-120-4616500

CART 0

• 0

MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping
`        The saturation current form a thoriated-tungsten cathode at 2000 K is 100 MA. What will be the saturation current for a pure-tungsten cathode of the same surface area operating at the same temperature? The constant A in the Richardson-Dushman equation is 60 × 10^4 A/m^2-K^2 for pure tungsten and 3.0 × 10^4 A/m^2-K^2 for thoriated tungsten. The work function of pure tungsten is 4.5 eV and that of thoriated tungsten is 2.6 eV.`
3 years ago

Deepak Patra
474 Points
```										Sol. i = AST2 e^-∅/KT
i base 1 = i i base 2 = 100 mA
A base 1 = 60 * 10^4 A base 2 = 3 * 10^4
S base 1 = S S base 2 = S
T base 1 = 2000 T base 2 = 2000
∅ base 1 = 4.5 eV ∅ base 2 = 2.6 eV
K = 1.38 * 10^–23 J/k
i = (60 * 10^4) (S) * (2000)^2 e^-4.5*1.6*10^-19 /1.38*10^-23 *2000
100 = (3 * 10^4) (S) * (2000)^2 e^-2.6*1.6*10^-19 /1.38*10^-23 *2000
Dividing the equation
i/100 = e^[-4.5*1.6*10/1.38*2 (-2.6*1.6*10/1.38*20)]
⇒ i/100 = 20 * e^-11.014 ⇒ i/100 = 20 * 0.000016
⇒ i = 20 * 0.0016 = 0.0329 mA = 33 μA

```
3 years ago
Think You Can Provide A Better Answer ?

## Other Related Questions on Electric Current

View all Questions »
• Complete Physics Course - Class 12
• OFFERED PRICE: Rs. 2,756
• View Details
Get extra Rs. 551 off
USE CODE: CHEM20
• Complete Physics Course - Class 11
• OFFERED PRICE: Rs. 2,968
• View Details
Get extra Rs. 594 off
USE CODE: CHEM20