3  CURRENT
ELECTRICITY
Page
1
1 )
Resistance
of
silver
wire
is
3
Ω
at
30
°
C
and
at
100
°
C,
it
is
3.5
Ω
.
Find its
temperature
coefficient
of
resistance.
[ March,
2003 ]
( Ans:
2.44
×
10


3
°
C

1
)
2 )
Resistance
of
a
wire
is
10.5
Ω
at
21
°
C
and
at
147
°
C
it
is
16.5
Ω
.
Find
its
temperature
coefficient
of
resistance.
[ April,
2002 ]
( Ans:
4.56
×
10


3
°
C
– 1
)
3 )
A
conducting
wire
has
a
resistance
of 20
ohm.
Its
length
is
now
stretched
to
increase
by
2 %.
Calculate
the
resulting
value
of
the
resistance
of
the
wire.
[ March,
2002 ]
( Ans:
20.8
Ω
)
4 )
5 metre
long
wire
is
connected
with
cell.
The
e. m. f.
and
internal
resistance
of
the
cell
are
2.5
V
and
0.5
Ω
.
The
resistance
of
wire
is
2
Ω
.
Find
the
potential
gradient
on
the
wire.
[ October,
1998 ]
( Ans:
0.4
V
/
m
)
5 )
Two
resistors
15
Ω
and
B
Ω
are
connected
in
parallel.
This
combination
is
connected
in
series
to
a
5
Ω
resistor
and
a
battery
of
e. m. f.
5
volt.
If
the
current
through
B
ohm
resistor
is
1
/
//
3
A,
find
the
value
of
B.
[ March,
1998 ]
( Ans:
7.5
Ω
ΩΩ
)
6 )
A
pyramid
is
constructed
from
six
conductive
wires
each
of
resistance
‘ R ’.
Calculate
the
effective
resistance
between
any
two
vertices of
the
pyramid.
( Ans:
R
/
2 )
[ October,
1997,
October,
1996 ]
7 )
Three
batteries
E
1
11
=
1.5
V,
E
2
22
=
2.5
V
and
E
3
33
=
3.5
V
and
a
resistance
R
=
10
Ω
are
connected
in
series
to
make
a
loop
of
closed
circuit.
In
this
E
2
and
E
3
are
in
helping
position
and
E
1
11
is
in
opposite
position.
Now
5
Ω
resistance
is
connected
in
parallel
to
E
2
.
Find
the
current
passing
through
10
Ω
and
5
Ω
resistance
and
battery
E
2
22
.
( Ans:
0.45 A,
0.5
A
and
0.95
A )
[ March,
1997 ]
8 )
An
electron of
mass
9
×
10
28
gm
and
charge
of
1.6
×
10
19
C
moves
in
a
conductor
with
acceleration
of
10
12
m
/
s
2
.
Find
potential
gradient
of
the
conductor.
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 Spring '06
 Smith
 Current, Resistance, Resistor, Electrical resistance, Ω

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