The number density of free electrons in a copper conductor estimated in Example 3.1 is 8.5 × 1028 m–3. How long does an electron take to drift from one end of a wire 3.0 m long to its other end? The area of cross-section of the wire is 2.0 × 10–6 m2 and it is carrying a current of 3.0 A.
Here, n=8.5×1028m−3,l=3.0m,A=2.0×10−6m2,I=3.0A,t=?n=8.5×1028m-3,l=3.0m,A=2.0×10-6m2,I=3.0A,t=? As, I=nAevd∴Vd=InAeI=nAevd∴Vd=InAe, Now, t=lvd=lnAeI=3.0×8.5×1028×2.0×10−6×1.6×10−193.0=2.72×104s=7t=lvd=lnAeI=3.0×8.5×1028×2.0×10-6×1.6×10-193.0=2.72×104s=7 hour 33 minute.
