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JEE Main Physics Class 12 Electric Charges and Fields Questions
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© examsnet.com
Question : 39
Total: 108
A cube of side '
a
' has point charges
+
Q
located at each of its vertices except at the origin where the charge is
−
Q
. The electric field at the centre of cube is :
24Feb2021 Shift1
3
Q
3
√
3
π
ε
0
a
2
(
∧
x
+
∧
y
+
∧
z
)
−
2
Q
3
√
3
π
ε
0
a
2
(
∧
x
+
∧
y
+
∧
z
)
2
Q
3
√
3
π
ε
0
a
2
(
∧
x
+
∧
y
+
∧
z
)
Q
3
√
3
π
ε
0
a
2
(
∧
x
+
∧
y
+
∧
z
)
Validate
Solution:
Electric field due to all charges will cancel out except two charges
+
Q
and
−
Q
placed along body diagonal.
→
E
−
Q
=
−
Q
4
π
ε
0
3
a
2
4
(
∧
x
+
∧
y
+
∧
z
)
√
3
→
E
+
Q
=
−
Q
3
π
ε
0
a
2
(
∧
x
+
∧
y
+
∧
z
)
√
3
Net electric field at the centre of cube is
→
E
net
=
→
E
−
Q
+
→
E
+
Q
=
−
2
Q
3
√
3
π
ε
0
a
2
(
∧
x
+
∧
y
+
∧
z
)
© examsnet.com
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