You are Here: Home >< Physics

# Synoptic Grapf Analogy watch

1. What does the lnN against time graph luk like..and its anonlagy with capacitors..Sfteee
2. Straight line through origin.

Intercept is [ln]No, and gradient = (-)[landa] i think

analogous with

capacitors
[ln]I against t
Were intercept equals Io, and gradient equals 1/RC
3. it obeys y=mx+c which is a stright line but it doesn't have to be through the origin depends if c is zero when x is zero or not so
the equation is N=N(initial)e^-λt
so by lenning both sides to get rid of e the equation becomes
ln N=lnN°-λt
y= c-mx
so lnN° is the y intercept the graph would be a stright decreasing line with a negative slop equals to -λ
4. The analogy with capacitors would be that the chrage left on a capacitor (capacitance C) discharging through a resistor (resistance R) would also lead to a straight line graph when you plot ln(Q) against time. Again this is because:

Q = Q0e-t/RC
lnQ = ln(Q0e-t/RC)
lnQ = lnQ0 - t/RC

y = mx + c

with y=lnQ, x=t, m= -1/RC and c = lnQ0

I think..
5. So The number of nuclei decayed is analogous with the charge in capacitor. that makes sence.

So that must mean that Current(dq/dt) is analogous with activity(dn/dt)??
6. (Original post by SinghFello)
So The number of nuclei decayed is analogous with the charge in capacitor. that makes sence.

So that must mean that Current(dq/dt) is analogous with activity(dn/dt)??
according to Q=Q°e^-t/RC
then λ≡1/RC
dQ/dt=Q/RC
same like dN/dt=Nλ
so dQ/dt=I
and dN/dt=A
now the voltage can be applied in the same equation as it's directly proportional to Q
but nothing indicates that it's anologous to any of the decay equation things
7. Sorted!

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: June 19, 2005
The home of Results and Clearing

### 1,054

people online now

### 1,567,000

students helped last year
Today on TSR

### IT'S TODAY!

A-level results chat here

### University open days

1. London Metropolitan University
Sat, 18 Aug '18
2. Edge Hill University
Sat, 18 Aug '18
3. Bournemouth University
Sat, 18 Aug '18
Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE